1. Exponential and Logarithmic functions

    A certain material decays at a rate of 1.9% per year. The sample is 260 grams. How much will be left in 11 years? How long will it take to have only a 100g sample left?
  2. calculus

    The rate at which an amount of a radioactive substance decays is modeled by the differential equation dA/dt = kA, where A is the mass in grams, t is the time in years, and k is a constant. Answer the following. a) If a 100-gram sample of the radioactive
  3. science

    As redioactive material decays and the percentage of new material in the original sample increases, does the age of the sample substance increase, decrease, or remain the same?
  4. Physics/Math

    A 25.0 gram piece of charcoal is found in some ruins of an ancient city. The sample shows a 14C activity, R, of 250 decays/min. How long (in years) has the tree this charcoal came from been dead? I think I have the use the equation: R=lamda*No*e^(-lamda*t)
  5. Pre Calculus

    If a 25 mg sample of radioactive material decays to 18.4 mg in 5 years, how long will it take the sample to decay to 20.5 mg?
  6. algebra 2

    In the formula A(t) = A0ekt, A is the amount of radioactive material remaining from an initial amount A0 at a given time t, and k is a negative constant determined by the nature of the material. An artifact is discovered at a certain site. If it has 72% of
  7. Algebra I

    A sample of radioactive material weighing 45 grams has a decay rate of 4.25% each day. The equation y = 45(2.7)–0.0425t can be used to find the amount of material that still remains, where t is the number of days that have passed. Approximately what is
  8. algebra

    Suppose a sample of Cesium-137 with initial mass of 200 grams decays to a mass of 160 grams voer the course of 10 years. Find the half-life of Cesium-137 (Round to the nearest year) How much Cesium-137 is left in the sample after 60 years? Round to the
  9. Chemistry

    It took 109.8 years for a 300.0 mg sample of an unknown radioactive material to completely disintegrate. Calculate the mass of the element (in grams/mole) assuming that the disintegrations per second are constant over the life-time of the sample, and the
  10. Physics!

    The activity of a sample of 35(upper#) 16(lower#)Sulfer (T 1/2= 7.55x10^6 s) is 2.51x10^5 decays per second. WHat is the mass of the sample? m= in grams PLease help me out...Thank you! :)
  11. Physics Plz help me

    The activity of a sample of 35(upper#) 16(lower#)Sulfer (T 1/2= 7.55x10^6 s) is 2.51x10^5 decays per second. WHat is the mass of the sample? m= in grams PLease help me out...Thank you! :)
  12. Physics

    The activity of a sample of 35(upper#) 16(lower#)Sulfer (T 1/2= 7.55x10^6 s) is 2.51x10^5 decays per second. WHat is the mass of the sample? m= in grams PLease help me out...Thank you! :)
  13. Physics Plz help me

    The activity of a sample of 35(upper#) 16(lower#)Sulfer (T 1/2= 7.55x10^6 s) is 2.51x10^5 decays per second. WHat is the mass of the sample? m= in grams PLease help me out...Thank you! :)
  14. chem

    the following procedure may be used to determine the density of a granular material. A sample of a granular material weighing 4.35 grams is placed in a 15 mL flask and then completely filled with benzene (liquid) the density of which is .879g/cc. The
  15. math

    Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t)=(.98)^t (b) Estimate the half-life of
  16. Physics

    A gram of living plant material with Carbon-14 , decays at a rate of about 16 disintegrations per minute. When the plant dies, the Carbon-14 decays, with a half-life of 5600 years. A gram of the dead plant is found to decay at about 1 disintegration per
  17. Pre-Calculus

    It is well known that superman can withstand as much as 3 grams of Green Kryptonite indefinitely. However, exposure to more than 3 grams for more than 13 hours is fatal. Assume that Kryptonite decays at an hourly rate of 5.35% If superman is trapped in a
  18. Physics: Fluids

    A sample of an unknown material weighs 260 N in air and 175 N when immersed in alcohol of specific gravity 0.700.
  19. math

    Brenda earns $14,260 per year. paid 24 times a year with 1 exemption. If $19.63 in taxes is withheld from each check at what rate is she taxed
  20. Algebra

    A sample of 600 grams of radioactive substance decays according to the function A(t)=600e^-0.045t where t is the time in years. How much of the substance will be left in the sample after 20 years? Round to the nearest whole gram. A 778 g B 1 g C 0 g D 244
  21. math check

    Brenda Luai earns $14,260 per year. She is paid 24 times per year and claims 1 exemption. If $19.63 in taxes is withheld from each paycheck, at what rate is she taxed?
  22. math

    Brenda Luai earns $14,260 per year. She is paid 24 times per year and claims 1 exemption. If $19.63 in taxes is withheld from each paycheck, at what rate is she taxed?
  23. Calculus

    A certain radioactive material decays exponetially. The percent, P, of the material left after t years is given by P(t)= 100(1.2)^-t a)Determine the half life of the substance
  24. NEED HELP WITH CALC

    Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t) = (b) Estimate the half-life of strontium.
  25. calculus

    Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t) = (b) Estimate the half-life of strontium.
  26. Math

    Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t) = (b) Estimate the half-life of strontium.
  27. Algebra please check my answers

    1) The linear function f(x) contains the points (-10, -29) and (-2, 83). If g(x) = 25x - 50, which statement is true? A. The functions f(x) and g(x) both have positive slopes.
  28. AP Calculus

    An Initial amount of 100 grams of Thorium-234 decays according to the model: dP/dt=-0.02828P (where t is measured in years). a) Find the equation for the amount of Thorium left after t years. b) Determine the half-life of this radioactive isotope c) How
  29. Chemistry

    In 6.20 h a 100 g sample of ag 112 decays to 25 grams. what is the half life of ag 112. I think the answer is 3.10 but I'm not sure. Thanks in advance =)
  30. Physics

    A sample of charcoal from an archaeological site contains 55 g of carbon and decays at a rate of .877 Bq. How old is it? ok I am totally lost, I don't know where to start
  31. physics

    A sample of charcoal from an archaeological site contains 55 g of carbon and decays at a rate of .877 Bq. How old is it? ok I am totally lost, I don't know where to start
  32. Chemistry

    Part 1 : a.) How many grams of Hydrogen will be contained in a 100.000 g sample of magnesium hydroxide.? c.) How many grams of nitrogen will be contained in a 120.0 g sample of calcium cyanide? ________________________________________ Part 3: d.) How many
  33. fin

    The following tabulation gives earnings per share figures for the Foust Company during the preceding 10 years. The firm’s common stock, 7.8 million shares outstanding, is now (1/1/03) selling for $65 per share, and the expected dividend at the end of the
  34. College Algebra

    Plutonium-238 is used in bombs and power plants but is dangerously radioactive. It decays very slowly into radioactive materials. If you started with 300 grams today, a year from now you would still have 297.6 grams. Construct an exponential function to
  35. Science

    If 15% of the radioactive material decays in 5 days, what would be the percentage of amount of original material left after 25 days?
  36. calc

    At what rate is the amount of material growing if bacteria in a sample increases to 250 when the sample is observed for 150 minutes?
  37. Pre-Calc

    Amount after time t A (t) = yobt Where: yo = starting amount b = growth constant (percent remaining) t = number of time units It is well known that superman can withstand as much as 3 grams of Green Kryptonite indefinitely. However, exposure to more than 3
  38. stat

    1. The amount of pyridoxine (in grams) per multiple vitamin is normally distributed with = 110 grams and = 25 grams. A sample of 25 vitamins is to be selected. So, 95% of all sample means will be greater than how many grams?
  39. statistics

    Seventy million pounds of trout are grown in the U.S. every year. Farm-raised trout contain an average of 32 grams of fat per pound, with a standard deviation of 7.5 grams of fat per pound. A random sample of 34 farm-raised trout is selected. The mean fat
  40. statistics

    Seventy million pounds of trout are grown in the U.S. every year. Farm-raised trout contain an average of 32 grams of fat per pound, with a standard deviation of 7.5 grams of fat per pound. A random sample of 34 farm-raised trout is selected. The mean fat
  41. Stat 1

    Seventy million pounds of trout are grown in the U.S. every year. Farm-raised trout contain an average of grams of fat per pound, with a standard deviation of grams of fat per pound. A random sample of farm-raised trout is selected. The mean fat content
  42. Math

    A 15-g sample of radioactive iodine decays in such a way that the mass remaining after t days is given by m(t) = 15e^(−0.051t), where m(t) is measured in grams. After how many days is there only 3 g remaining?
  43. College Algebra

    A 15-g sample of radioactive iodine decays in such a way that the mass remaining after t days is given by m(t) = 15e−0.051t, where m(t) is measured in grams. After how many days is there only 1 g remaining?
  44. math

    10/20 + 11/13 I know I have to first find the LCM which is 260. Then I found the equivalent fractions which were 130/260 and 220/260. When I add those I get 350/260 which is an improper fraction. Then I change that to a mixed number fraction. The answer I
  45. chemistry

    A radioactive sample contains 3.25 1018 atoms of a nuclide that decays at a rate of 3.4 1013 disintegrations per 26 min. (a) What percentage of the nuclide will have decayed after 159 d? % (b) How many atoms of the nuclide will remain in the sample? atoms
  46. physics

    If the mass of a material is 102 grams and the volume of the material is 21 cm3, what would the density of the material be?
  47. Math

    A radioactive material has a half life of 500 years. A) Given 20 grams of this material, how much will remain after 1,000 years? B) Given 100 grams of this material, how much will remain after 750 years? Thank you to whom ever can help me :)
  48. physics

    1)7Be decays with a half-life of about 53 d. It is produced in the upper atmosphere, and filters down onto the Earth's surface. If a plant leaf is detected to have 300 decays/s of 7Be, how many days do we have to wait for the decay rate to drop to 13.6/s?
  49. Chemistry/Engineering

    A 25 gram sample of CT is vaporized and used to fill a 5 L container. If the pressure in the container is 1.2 atm at 27 degrees Celsius, what is the molecular weight of CT in grams per mole? I used PV=nRT and found n=.2437 mol, but how do I got to grams
  50. earth science

    If the mass of a material is 76 grams and the volume of the material is 23 cm3, what would the density of the material be?
  51. Science

    A girl makes a sample of a new material and says that the density of the material is 0.85 g/cm. Can you tell how large a sample she made? How?
  52. math

    Your optimal exercise heart rate for cardiovascular benefits is calculated as follows: Subtract your age from 220 and then find 80% of the difference. the rate for a 40 year old is 144 and the rate for a 10 year old 168 Rounded to the nearest whole number,
  53. Physics

    The activity of a sample of 31Si (T1/2 = 9.43×103 s) is 7.88×105 decays per second. What is the mass of sample present?
  54. Physics Help Please

    A sample of an unknown material appears to weigh 270 N in air and 165 N when immersed in alcohol of specific gravity 0.700. (a) What is the volume of the material? (b) What is the density of the material?
  55. Physics

    A sample of an unknown material appears to weigh 275 N in air and 160 N when immersed in alcohol of specific gravity 0.700. What is the volume of the material? What is the density of the material?
  56. Physics Help Please

    archaeologist digging at the site of an ancient settlement discover the remains of a wooden structure. carbon 14 dating of the wood from the structure finds a decay rate of 180 decays/min. Knowing that the decay rate for living wood is 600 decays/min and
  57. Physics Help Please! Decay Questions

    archaeologist digging at the site of an ancient settlement discover the remains of a wooden structure. carbon 14 dating of the wood from the structure finds a decay rate of 180 decays/min. Knowing that the decay rate for living wood is 600 decays/min and
  58. Chemistry

    In a series of decays (hypothetical), the nuclide Ra-227 beomes Pb-203. How many alphas and how many betas are emitted in this series? Give two answers: first, give the number of alpha decays; then, the number of beta decays. I know that there are 6 alpha
  59. chemistry (NEED HELP)

    In a series of decays (hypothetical), the nuclide Ra-227 beomes Pb-203. How many alphas and how many betas are emitted in this series? Give two answers: first, give the number of alpha decays; then, the number of beta decays. I know that there are 6 alpha
  60. chemistry (need some help)

    In a series of decays (hypothetical), the nuclide Ra-227 beomes Pb-203. How many alphas and how many betas are emitted in this series? Give two answers: first, give the number of alpha decays; then, the number of beta decays. I know that there are 6 alpha
  61. FINANCE 200

    You receive $5000 three years from now. The discount rate is 8 percent. What is the value of your investment two years from now? (Multiply 5000 by .926 (one year discount rate at 8%) Will it be worth $9,260?
  62. physics

    Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the half-life is 22 hrs? What is the initial activity of the sample in decays per minute?
  63. MATH Precalculus

    1) A radioactive substance decays exponentially. A scientist begins with 150 milligrams of a radioactive substance. After 26 hours, 75 mg of the substance remains. How many milligrams will remain after 46 hours? 2) A house was valued at $110,000 in the
  64. Pre Calculus

    Exponential growth and decay find the half life of a radioactive substance if 220 grams of the substance decays to 200 grams in 4 years?
  65. Chem

    . State whether each of the following samples of matter is a gas. If there is not enough information for you to decide, write "insufficient information." (a) A material is in a steel tank at 100 atm pressure. When the tank is opened to the atmosphere, the
  66. present annuity

    What is the present value of an annuity that consists of 28 monthly payments of $260 at an interest rate of 8% per year, compounded monthly? (Round your answer to the nearest cent).
  67. Chemistry, Physics (Radiation Toxicology)

    a) Na-22 decays in two ways. In 100 atoms of Na-22 decaying, how many would decay by positron emission and how many would decay by electron capture? Why is the yield of photon gamma (+/-) so high? b) In 100 decays of Ra-226, how many decays would result in
  68. Pre Calculus

    Tritium, a radioactive isotope of hydrogen, has a half-life of 12.4 years. Of an initial sample of 69 grams, how much will remain after 75 years? a. 1.5848 grams b. 61.5289 grams c. 0.0000 grams d. 1.0426 grams e. 17.2500 grams
  69. Pre Calculus 1

    thirty percent of a radioactive substance decays in four years. assuming the decay is exponential, find the half life of the substance. the beginning of 1975 the population of a country was 40 million and growing at a rate of 3% per year. Assume that the
  70. physical science

    If the mass of a material is 99 grams and the volume of the material is 22 cm3, what would the density of the material be? (in g/cm3) i don't know how to find the answer.
  71. precalc

    I am really struggling with a bunch of problems. Any help with any of the following would be greatly appreciated. Thanks 1. ln e^(ln x) - ln(x - 3) = ln 8 2.3e^(6x - 2) = 18 The word problems, especially, are killing me. 3. In the formula A = Iekt, A is
  72. Calculus

    Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t)=?
  73. chemistry

    1.How many atoms are in a sample of copper with a mass of 18.46 grams? 2.How many formula units are in a sample of salt with a mass of 67.69 grams? 3.How many molecules are in a sample of water with a mass of 44.99 grams? 4.What is the mass in grams of
  74. chemistry

    1.How many atoms are in a sample of copper with a mass of 18.46 grams? 2.How many formula units are in a sample of salt with a mass of 67.69 grams? 3.How many molecules are in a sample of water with a mass of 44.99 grams? 4.What is the mass in grams of
  75. Word Problems-Math

    Please help with my word problems? Solve the problem. The rabbit population in a forest area grows at the rate of 6% monthly. If there are 260 rabbits in April, find how many rabbits (rounded to the nearest whole number) should be expected by next April.
  76. Algebra-Problems

    Please help with my word problems? Solve the problem. The rabbit population in a forest area grows at the rate of 6% monthly. If there are 260 rabbits in April, find how many rabbits (rounded to the nearest whole number) should be expected by next April.
  77. math/algebra

    Use the exponential decay equation, to find the half-life of a material that decays from 40mg to 30mg in 10 hours.
  78. Nuclear physics

    1)7Be decays with a half-life of about 53 d. It is produced in the upper atmosphere, and filters down onto the Earth's surface. If a plant leaf is detected to have 300 decays/s of 7Be, how many days do we have to wait for the decay rate to drop to 13.6/s?
  79. physics

    A sample of an unknown material appears to weigh 285 N in air and 165 N when immersed in alcohol of specific gravity 0.700. (a) What is the volume of the material? Answer is in m3 (b) What is the density of the material? Answer is in kg/m3
  80. Mortgage Class

    A borrower received a 30-year ARM mortgage loan for $120,000. The start rate was 3.50% and the loan adjusts every 12 months for the life of the mortgage. Rate caps are 3/2/6. The index used for this mortgage is the LIBOR. For this exercise, let’s say it
  81. chemistry

    Examine the information. Isotope B has a half-life of 3 days. A scientist measures out 100 grams of this substance. After 6 days has passed, the scientist reexamines the sample. How much of Isotope B will remain in the sample? 100 grams 63 grams 94 grams
  82. Math - Exponential Decay

    Radium decays exponentially. Its half-life is 1,690 years. How long will it take for a 50-gram sample of radium to be reduced to 5 grams? 1/2P = Pe^(-1690k) (ln1/2)/(-1690) = k 4 x 10^-4 = k 5 = 50e^-kt ln0.1 = -kt ln0.1/-k = t 5,630 years = t ...but
  83. Pre Cal

    a radio actice substance decays so that half of the substance decays every 2 minutes. if 100 g of the substance are present initially, how many grams will be present after 4 minutes and 8 minutes respectively?
  84. physics

    If the mass of a material is 95 grams and the volume of the material is 14 cm3, what would the density of the material be? 6.785 g/cm3?
  85. chemistry

    Calculate the residence time of sodium in millions of years if the total amount of sodium in the oceans is 1.5 x 10 to the 22 grams, and is supplied to the ocean at a rate of 2.2 x 10 to the 14 grams per year.
  86. stat

    AluminiCorp is a major producer of aluminum cans that produces 40 billion aluminum cans every year. You work as a quality control officer for AluminiCorp, and are responsible for ensuring that the aluminum cans produced meet certain specifications. Each
  87. algebra

    Julie has 250 grams of a radioactive substance. The substance decays every hour. How long will it take until she has 20 grams of the substance left?
  88. Ap chemistry

    if a 84g sample of thorium decays with a 10 minute half life, how much would the sample weight in a half hour?
  89. modern physics

    A radioisotope P has a half-life of 3 s. At t = 0, a given sample of this isotope contains 8000 atoms. Calculate (i) its decay constant, (ii) average life, (iii) the time t1 when 1000 atoms of the isotope P remain in the sample, and (iv) number of decays
  90. ENGLISH

    You'll be alert, engrosed in the (14)material.And concentrated 100 percent. a) no change b) material, and c) material; and d) material and After reading it over and over, I think b) a comma after material would be the correct answer. I think this is a
  91. Chemistry

    Calculate the mass in grams of the undiluted bleach that was in the sample of bleach titrated. Given: Density of undiluted bleach unkown is 1.042 g/mL. 14.44 mL of .100 M Na2S2O3. .0537 grams of NaClO. Each sample should conain 1/5 of the original
  92. Physics II

    A 51.0 g sample of a conducting material is all that is available. The resistivity of the material is measured to be 12 10-8 · m, and the density is 7.67 g/cm3. The material is to be shaped into a solid cylindrical wire that has a total resistance of 1.5
  93. physics

    A 50.0-g sample of a conducting material is all that is available. The resistivity of the material is measured to be 11~ 10-8 ƒ¶m and the density is 7.86 g/cm3. The material is to be shaped into a solid cylindrical wire that has a total resistance of
  94. Economics

    A city must decide whether to build a downtown parking garage and what rate to charge. It is considering two rates: a flat $1.50-per-hour rate or an all-day rate averaging $1 per hour (based on a $10 daily rate and an average 10-hour stay). Parking demand
  95. macroeconomics

    The interest rate were zero under the old government.The GDP is $700 and at that time people kept a total of $120 in cash stored as well as %50 worth of bonds. However, under new government the interest rate has risen to 36%. On average, cash is used five
  96. math

    A custom order requires 13 1/4 grams of material that costs 11 1/2 ¢ per gram. Find the total cost of the material.
  97. physics

    thanks for the help earlier just got a question I'm taking AP Physics B this year does that mean next year I would Take AP Physics C??? I don't know if the material in C convers the same material plus the additional calculus material or what??? Could I
  98. Statistics

    A simple random sample of 50 female 14-year-olds is selected. The sample mean height of the girls is found to be 62 inches. Assume the height of 14-year-old girls is normally distributed with a standard deviation of 5 inches. 1. Based on these data, a 95%
  99. chemistry

    Please help me through this problem... A 0.5117 gram fertilizer containing phsphorus was oven dried. The weight of the dried sample is 0.4998 grams. However, 10% moisture is still retained in the sample. Calculate the moisture content in the sample in as
  100. economics

    Jerry will receive the following payments: 946 in year 3, 929 in year 5 and 958 in year 9. What is the purchasing power of the present value of these payments if the market interest rate is 17% per year and the inflation rate is 6% per year?