# Posts by jane

Total # Posts: 1,651

**Science**

Can anyone help me find the half-life of strontium-90? I also need an explanation on how to do it. Thanks!! Radioactive Decay of Strontium-90: At 0 years: 100% remaining At 28 years: 50% remaining At 56 years: 25% remaining At 84 years: 10% remaining At 112 years: 5% remaining.

**Chemistry**

How many moles of NH3 must be added to 1.00 L of solution to dissolve 0.979 g of CuCO3? For CuCO3, Ksp = 2.3 × 10-10.

**Math**

A military plane maintains an altitude of 15,000 feet over a vast flat desert. It flies at a constant speed on a line that will take it directly over an observer on the ground. At noon, the angle of elevation from the observer’s shoes to the plane is 30 degrees, and the ...

**algebra**

Solve.(Find all complex-number solutions.) 12t^2 + 17t = 40

**algebra**

How do I solve for this: F = Av^2/400, for v (force of wind on a sail).

**Math**

i still don't understand how you did all of them. can you please elaborate? the answers for #2 is supposed to be 5.728 ft/min and #3 is 3.59in/min

**Math**

Please help. I have the answers to these problems but I'd like to know how to solve it step by step. 1. Air is being pumped into a spherical balloon at the rate of 1.754 cubic centimeters per second. The balloon maintains a spherical shape throughout. How fast is the ...

**Math**

What is a “real” zero? 1. A solution to a polynomial. 2. A non-imaginary number. 3.An x-intercept of a polynomial. 4. All of the above. The answer is 4, right?

**Accounting**

Complete the following exercise. In December 20X2, the Cardoso Company established its predetermined overhead rate for jobs produced during the year 20X3 by using the following cost predictions: Overhead costs: $750,000 Direct labor costs: $625,000. At year-end 20X3, the ...

**Accounting**

Complete the following exercise. Fill in the Excel spreadsheet provided via the link below to provide your answers to parts a and b. Then paste the Excel data into a Word document on which you can also write the answer to part c. Income Statement Administrative Expenses $ 70,...

**Chemistry**

Calculate one Al(OH)3 formula unit in grams/unit. I keep arriving at the answer of 1.295 x 10-22 g/unit but my homework says it is incorrect! SOMEONE please help!!!

**Chemistry.**

Okay, thanks. Do I always round up to the nearest whole number?

**Chemistry.**

Give the empirical formula of each of the following compounds if a sample contains the following quantities of each element. (a) 0.0091 mol C, 0.0186 mol H, and 0.0045 mol O Please show me how to do this. My notes are very confusing and I don't know how to apply them to ...

**Physics**

Thank you so much!

**Physics**

"A moving object has a kinetic energy of 145 J and a momentum with a magnitude of 40.0 kg·m/s. Determine the mass and speed of the object." I simply cannot figure it out. I know that KE=.5mv^2 and that p=mv but I can't seem to piece it together. Please ...

**History**

It's D!!!!!

**math**

The weekly marginal cost functions C'(x) and the weekly marginal revenue function R'(x) of a company assembling personal computers are given by C'(x) =RM(3x^2-118x+1315) and R'(x)=RM(1000-4x), where x is the number of computers assembled per week. If the fixed ...

**Maths**

If the 6th term of an arithmetic sequence is 48, and the sum of the first 6 terms is 300, what is the first term and the constant difference?

**ALGEBRA**

If I pay RM200 every month for 20 years into an investment account that gives 3% p.a interest compounded monthly, how much will I get at the end of 20 years?

**ALGEBRA**

if the 6th term of an arithmetic sequence is 48, and the sum of the first 6 term is 300, what is the first term and the constant difference? Pls help as I have never learn this before,need some example to start with.thank you

**math**

three partitions and x is shown as dimension of a partition

**calculus**

The position, in feet, of a target is given by s(t)=250-3t+9t^2+2t^3, where t is the time in seconds. The origin of coordinates is at the point where an observer stands, and the positive direction of movement is that one pointing EAST from the origin. What is the initial ...

**Calculus angle of elevation**

A man is walking towards a wall at 3 ft/sec while looking at a picture on the wall, at a height of 5 feet from the floor. How is the angle of observation changing when the man is 8 feet away from the screen.

**Physics HELP!**

A 50-g mass is attached to a spring and undergoes simple harmonic motion. Its maximum acceleration is 15m/s2 and its maximum speed is 3.5m/s . Determine the angular frequency. Determine the spring constant. Determine the amplitude of the motion. how do I find these things?

**Euler's method help in Calculus?????**

Let dy/dx=xy . Use Euler's method with step size of 0.5 and the initial condition of y(0) = 3 to estimate y(2). I really am not sure if I did this right, but I got 3.4568 for y(2). I actually feel like it is wrong.

**L'Hopitals Rule**

5) Use the L’Hopital’s method to evaluate the following limits. In each case, indicate what type of limit it is ( 0/0, ∞/∞, or 0∙∞) lim x→2 sin(x^2−4)/(x−2) = lim x→+∞ ln(x−3)/(x−5) = lim x→pi/4...

**MATH EMERGENCY I HAVE 10 MINUTES**

A supplier of portable hair dryers will make x hundred units of hair dryers available in the market when the unit price is p = sqrt(49 + 4.4x) dollars. Determine the producers' surplus if the market price is set at $15/unit. (Round your answer to two decimal places.)

**MATH CALC**

A supplier of portable hair dryers will make x hundred units of hair dryers available in the market when the unit price is p = sqrt(49 + 4.4x) dollars. Determine the producers' surplus if the market price is set at $15/unit. (Round your answer to two decimal places.)

**math Calc**

The management of the Titan Tire Company has determined that the quantity demanded x of their Super Titan tires/week is related to the unit price p by the relation p = 172 − x^2 where p is measured in dollars and x is measured in units of a thousand. Titan will make x ...

**Chemistry**

The solubility product constant of BaF2 is 1.7 x 10^-6 forgot to put that

**Chemistry**

The concentration of fluoride ions in a saturated solution of barium fluoride is __________ M. The solubility product constant of BaF2 is ???

**calc**

The demand function for a certain make of replacement cartridges for a water purifier is given by the following equation where p is the unit price in dollars and x is the quantity demanded each week, measured in units of a thousand. p = -0.01x^2 - 0.3x + 19 Determine the ...

**cal**

The demand function for a certain make of replacement cartridges for a water purifier is given by the following equation where p is the unit price in dollars and x is the quantity demanded each week, measured in units of a thousand. p = -0.01x^2 - 0.3x + 19 Determine the ...

**Chemistry**

Consider the following reaction, equilibrium concentrations, and equilibrium constant at a particular temperature. Determine the equilibrium concentration of H2O(g). C2H4(g) + H2O(g) C2H5OH(g) Kc = 9.0 × 103 [C2H4]eq = 0.015 M [C2H5OH]eq = 1.69 M

**Math**

I'm so sorry. That was the answer to the problem that I'm trying to solve. The actual problem is (5x^3-x^2+20t-8)/((x^2+4)^2) I would like to know how to solve it step by step

**Math**

Correction: ((5x-1)/(x^2+4)) - ((4/(x^2+4)^2))

**Math**

write the partial fraction decomposition step by step ((5x-1)/(x^2+4)) - ((4)/(x^2+4)^2)

**Math**

write the partial fraction decomposition step by step (-5x^2-8x-3)/(x^3+x^2+x)

**Math**

Wait where the heck did you get 5/10 from

**Physics**

A box is sitting at rest at the top of a ramp 3.00m long at an angle to the horizontal of 12 degrees. When the box reaches the bottom of the frictionless ramp, it falls an additional 2.00 m vertically before hitting the floor. How far from the right end of the ramp does the ...

**english**

Compare Robert Fulghum’s list of things learned in kindergarten (see the Connection on page 72) to Franklin’s list of virtues. Which list do you think would be more useful to people today? In general, how does Franklin’s scheme for moral perfection compare with ...

**History (1 word)**

DrBob222.. Don't reply if you aren't gonna answer it(:

**History (1 word)**

What word expresses the idea that a state could declare that federal legislation unconstitutional and could disregard it?

**Programming (Integer generator)**

Write a program that accepts two numeric values from the user and displays all integers between these values. Your program will Accept a starting value Accept an ending value Display all the integers (inclusive) between those two values. Your program should count up or down (...

**Chemistry**

dH1 i got -890 kJ/mol dH2 i got -1411 kJ/mol

**Chemistry**

I tried to use how you answered for someone else but I got it wrong and used all my tries so I would like the real answer to see where I went wrong! Thanks for your consideration!

**Chemistry**

A 10.0 gram sample of a mixture of CH4 and C2H4 reacts with oxygen at 25°C and 1 atm to product carbon dioxide gas and liquid water. If the reaction produces 520 kJ of heat, what is the mass percentage of CH4 in the mixture? I am all out of tries on the homework, but I ...

**Pre-calc**

If Theta= -7pi/6; then cos(Theta) is...

**CHEMISTRY!!!!! HELP!!**

high school level

**CHEMISTRY!!!!! HELP!!**

I'm looking for a chemistry and applied chemistry textbook that had been published between 2011-2014. Please help because I couldn't find one on google.

**CALCULUS**

Hi guys can you help me! Please teach me step by step.. I really need it. pls! Thank you......... A swimming pool is 12 meters long, 6 meters wide, 1 meter deep at the shallow end, and 3 meters deep at the deep end. Water is being pumped into the pool at ¼ cubic meter ...

**Math**

Which group names all the whole number factors of a composite number? A. 1, 2, 3, 6, 9, 36 B. 1, 3, 5, 9, 45 C. 1, 3 D. 1, 2, 3, 4, 6, 8, 12, 24

**history**

1.c 2. d 3. d 4. a 100

**physics**

5. A woman is wearing her seat belt while driving 95km/h. She finds it necessary to slam on her brakes, and she slows uniformly to a stop in 5 s. Calculate the average force exerted on her by the seat belt (neglecting friction with the seat)? Express the result as a multiple ...

**physics**

An arrow is aimed horizontally, directly at a target 20.6 meters away. when the arrow is released, it lands 0.095 meters below the target point. a) How long was the arrow in the air? b) How fast was the arrow moving when it left the bow?

**physics**

You and your friend are on the roof of a 20 m tall building investigating a free fall. Your friend releases a small rock from rest. You throw another rock simultaneously with your friend aiming it straight down. (a) What initial speed should you supply to the rock so it hits ...

**English**

I need to create a diagram of hell similar to Dantes Inferno. What punishments would teach the following sins a lesson: Liars Thieves Cheaters Abusers Kidnappers Traitors Murderers Fraudsters Assualters

**physics**

A pot with a flower falls out of a window box in a tall apartment building. It passes the top of a particular window with a velocity of -1.7 m/s. It passes the bottom of this window 0.2800 s later? How tall is the window (watch sign)?

**Chemistry**

Please help! Calculate the standard change in enthalpy, ΔH°rxn, for the decomposition of calcium carbonate to calcium oxide CaCO3 (s) → CaO (s) + CO2 (g) Given that: ΔH°f CaCO3 (s) = -1206.9 kJ/mol ΔH°f CaO (s) = -635.1 kJ/mol ΔH°f CO2...

**physics**

A ball falls 5.00 m to the ground. It remains in contact with the ground for 0.027 s and then rebounds to a maximum height of 1.61 m. What acceleration did the ball experience while it was in contact with the ground?

**physics**

A hot-air balloon is rising upward with a constant speed of 2.35 m/s. When the balloon is 2.50 m above the ground, the balloonist accidentally drops a compass over the side of the balloon. How much time elapses before the compass hits the ground?

**Physics**

An object is launched at an angle of 24 degrees above the horizontal at a velocity of 33.7 m/s from the top of a building which is 110.8 meters above the ground. When the object lands on the ground, what is the horizontal displacement from the base of the building in meters? ...

**chem**

A .7567 impure KHP was dissolved in water. 26.7 ml of standardized 0.068 M NaOH was used to achieve a phenolphthalein end point. The stoichiometric ratio between KHP and NaOH is 1:1. What is the percent by mass of KHP in the sample?

**Math**

cos 60 = 1/2 sin 60

**chem**

a 50ml aliquot sample of vinegar is titrated with a 0.078 M NaOH sol'n. The phenolpthalein end point was reached after the addition of 35.6 ml. Equation: HC2H3O2 + NaOH _____> NaC2H3O2 + H20 Calculate the % by mass/vol. of acetic acid in the sample.

**sociology**

in order to establish society, humans agree to obey certain rules.

**physics**

To what temperature must you raise a copper wire, originally at 20.0°C, to double its resistance, neglecting any changes in dimensions? (Does this happen in household wiring under ordinary circumstances?)

**physics**

The resistivity of silver is 1.59 × 10-8 Ω·m. What is the resistance of a section of 12 gauge wire (diameter 0.2057 cm) that is 8.60 m long?

**BASIC ACCOUNTING**

paid two months rent deposit and one month advance, P40,500

**Maths Help!!**

Melisa used 0.6kg of red sand to make a mural on the wall. She added 250g of blue sand to it. Finally she added 500g of white sand to half of the mixture. Find the mass of the mixture that has white sand in it. Express your answer in kilogram

**Maths**

In a basket, 3/4 of the fruits are oranges and the rest are apples. After I have away 10 oranges, there are now 1/2 as many oranges as apples. How many apples and oranges are there in the basket?

**Maths - Optimisation**

Thank you so much for your help on this :) Just a question though.. After you say y = 2x, you sub in y as 4x? ie. =(x^2+4x^2)^(1/2) where did the '4x' come from?

**Maths - Optimisation**

I've been trying to work out this question for hours and I can't seem to figure it out. Question: "Point 'A' is situated in the bottom left hand corner of a vertical rectangle with the dimensions 6m x 3m. Point 'B' is situated in the opposite top ...

**Chemistry**

Calculate PH of 0.05 M solution of ammonium acetate

**Math**

got it. thank you so much!

**Math**

how did you get appr 171.9° in the first question?

**Math**

Not really, can you go through it with me?

**Math**

If A=<2,1> and B=<-1,1>, find the magnitude and direction angle for -2A +3B Find all specified roots: Cube roots of 8i A parallelogram has sides of length 32.7cm and 20.2cm. If the longer diagonal has a length of 35.1cm, what is the angle opposite this diagonal?

**Math**

how can i put that in the form of A cos B (t- C)+D and A sin B (t- C)+D?

**EPIDEMIOLOGY**

A case-control study of the relationship between liver cirrhosis and alcohol use. In this study, smoking is associated with drinking alcohol and is a risk factor for liver cirrhosis among both non-alcoholics and alcoholics. Explain whether smoking is a confounder.

**Physics**

I finally got #3!

**Physics**

Actually, I have 3 questions to solve. I know the 1st one requires Coulomb's constant, but I just can't get the formula to work. Ditto for the formulas for the other 2 questions. 1) A 6.3 μC point charge and a −1.7 μC point charge are separated by a ...

**Physics**

I don't understand what the "^2" means or how to use it in the equation.

**Physics**

I have the 1st two answers, I just don't know how to calculate the other two. Everything I have tried comes out with a wrong answer. (a) 479.04e+8 m/s2 (b) 7.30627923e-7 s (c) m (d) J

**Physics**

A proton with mass 1.67×10−27 kg and charge 1.60×10−19 C accelerates from rest in a uniform electric field of strength 500 N/C. (a) What is the magnitude of the acceleration of the proton? (b) How long does it take the proton to reach a speed of 35,000 ...

**Math**

The 8th term of a g.p is -7/32 fine it's common ration if its first term is 28

**Physics**

You and a friend are playing a game of squirt-gun tag in a maze. Suddenly you see your friend's image in a small planar mirror (see illustration). You take a shot over the barrier in front of you and find that your friend is just at the end of the 7.0 m range of your ...

**Algebra**

multiply (n^3+8)(n-4) can you give me an example on how to solve this please

**physics**

A motor boat whose speed is 2.6 m/s in still water, needs to point upstream at an angle of 28.5 in order to travel straight across the river. Calculate the speed of the current and the resultant velocity of the boat across the river.

**MATH**

what is answer of this problem set X={X/X IS A BOY}

**Algebra**

solve grafically 3x-y=8, 6x-2y=8

**Algebra**

solve the problem grafically, 4y=x+4, x=2/3y+8/3

**Physics**

Show that the x-component of the tension force Fc in terms of its magnitude Fc is given by -0.3420 Fc

**Physics**

The length of a box is reduced to two third of its original value and the width and height are tripled. Calculate the factor by which the volume has changed. Am I on the right track? If not please help I am stuck. Thanks. V=LWH V=(L-2/3)(3W)(3H)

**geometry**

A hemispherical dome holds a volume of 486π..find the surface area (omit the area of the circle)? I just need the formulas id use

**Cosine Law NEED HELP QUCIK**

The minute hand of a clock is 12 cm long, and the hour hand is 10cm long. Determine the distance between the tips of the hands at 9:30pm, to the nearest mm. The answer is 17.5 cm I need to work on how to get to that answer!

**Cosine Law NEED HELP QUCIK**

For the next three questions, choose which is the most appropriate method to solve the problem, explain your answer. a) SOACAHTOA b) The Sine Law c) The Cosine Law d) The problem cannot be solved without further information 1) Yachts in a race have to sail a triangular course...

**7th grade science**

Energy & Environment Which of the following desribes an example of land reclamation? A)after an are is mined for copper ,the soil is replaced and new plants are planted. B)after a forest is clear-cut ,desertifications occur. C)after a forest is clear-cut,it is mined for copper...

**Cosine Law**

For the next three questions, choose which is the most appropriate method to solve the problem, explain your answer. a) SOACAHTOA b) The Sine Law c) The Cosine Law d) The problem cannot be solved without further information 1) Yachts in a race have to sail a triangular course...

**Cosine Law**

The minute hand of a clock is 12 cm long, and the hour hand is 10cm long. Determine the distance between the tips of the hands at 9:30pm, to the nearest mm.