# Posts by Zach

Total # Posts: 401

**Finite**

An urn contains 5 white balls and 4 black balls. If 3 balls are randomly selected ( at once, without replacement ), what is the probability that at least 1 ball is black? Give answer as a decimal number with three correct decimal places.

*November 14, 2013*

**math**

arrays and an expanded algorithm 23 x17 how do I solve this

*November 5, 2013*

**calculus and vectors**

------------------------------------- \.56 degree ...........45 degree.../ \................................/ \............................../ \............................/ \........................../ \......................../ \______________________...

*September 26, 2013*

**calculus and vectors**

Reiny, I do not see how your calculation = 65.88, I get 25.2. Also, I do not understand your diagram. It looks like this ------------------------------------- \ 56 degree 45 degree / \ / \ / \ / \ / \ / \______________________/ | | | 35 newtons | | | |_____________________|

*September 26, 2013*

**probability**

A random sample of six integers in the interval [1,42] is to be drawn. The numbers are selected randomly, one after the other, and repeats are allowed. What is the probability the six numbers in the sample will all be different?

*September 4, 2013*

**math**

A very small population consists of 7 units, labeled a; b; c; d; e; f; g. How many different samples of size 3 are there, for sampling without replacement, assuming that (a) samples are lists of units. (b) samples are sets of units.

*September 3, 2013*

**Biology**

What does the notation 4n = 28 tell you about how many types of chromosomes there are and how many of each type of chromosome are present in a cell? I am a little confused on how this is determined. Would it be 4 sets of chromosomes with 7 of each type of chromosome?

*August 24, 2013*

**math**

Shelly delivers the weekly local paper to neighborhoods in her town. House numbers are even on one side of the street and odd on the other. Shelly delivers an equal number of papers to both sides of the street. Although she always aims for the front doorstep, Shelly typically ...

*July 21, 2013*

**math**

Kalil flipped a coin sixty times. He got thirty-four heads. How does this result compare to the number of heads you would have expected based on theoretical probability?

*July 18, 2013*

**math**

Shelly delivers the weekly local paper to neighborhoods in her town. House numbers are even on one side of the street and odd on the other. Shelly delivers an equal number of papers to both sides of the street. Although she always aims for the front doorstep, Shelly typically ...

*July 18, 2013*

**MacroEconomics**

12

*July 15, 2013*

**algebra 1**

What is the solution set of the given equation? 4y - 6y + 9y = -2

*July 13, 2013*

**algebra 1**

Which of the following equations has the given solution set? Solution set: Ø

*July 13, 2013*

**algebra 1**

Which of the following would eliminate the variable on the left side of the given equation? 36 - 19w = -6w + 41

*July 13, 2013*

**Physics**

A tennis ball may leave the racket on a serve by a top player with a speed of 45.0 m/s. If the ball's mass is 0.063 kg, and it is in contact with the racket for 0.030 s, what is the average force (in newtons) on the ball?

*July 12, 2013*

**Physics**

A 17000 kg railroad car travels along on a level frictionless track with a constant speed of 23.0 m/s. A 5100 kg additional load is dropped onto the car. What then will be its speed in meters/second?

*July 10, 2013*

**Math**

Yes what I meant is that it decreased 1/4 of every its impact, so therefore the answer would be 60 mph after first impact.

*May 6, 2013*

**Math**

A rubber ball is thrown straight down from a height of 244 feet at speed of 80 feet per second. If the ball always rebounds with one-fourth of its impact speed, what will be the speed of the ball the third time it hits the ground? My Answer is: 1/4*80=60 1/4*60=45 1/4*45=33.75...

*May 6, 2013*

**Math**

I have 5 tickets for a raffle and I know that the probability of my winning the prize is 0.003. How many tickets were sold altogether?

*April 23, 2013*

**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?

*April 22, 2013*

**accounting**

I hate accounting and this class is trash

*April 14, 2013*

**6th grade math**

How to figure if 60 cookies were baked and 7/12 were given away, how many are left?

*April 9, 2013*

**chemistry**

When 1988 J of heat energy is added to 47.5 g of hexane, C6H14, the temperature increases by 18.5 °C. Calculate the molar heat capacity of C6H14.

*April 7, 2013*

**Physics**

A laser beam is being shot through two different materials that have been stuck together. if theta 1 = 65.5 and theta 2 = 49.8 what is the index of refraction? (I got 1.2 which is correct) but cant get part 2 PART 2~ If the index of refraction of n3 is 3.6, what is the final ...

*April 4, 2013*

**POETRY, PART 2**

#20

*March 7, 2013*

**math**

How do I find this integral using weierstrass substitution? 1/(9-4((sinx)^2))

*March 1, 2013*

**math**

How do I find this integral using weierstrass substitution? 1/9-4((sinx)^2)

*March 1, 2013*

**Organic Chemistry**

I am trying to figure out if I am correct about the solubility of 9-fluorenone in NaOH and diethyl ether and the solubility of benzoic acid in NaOH and diethyl ether 9-fluorenone is soluble in diethyl ether because it can hydrogen bond with water so it is soluble in the ...

*February 18, 2013*

**math**

from a square piece of cardboard with length and width of x inches, a square of width x-1 inches is removed from the center. Write the area of the remaining piece of cardboard as a function of x

*February 13, 2013*

**Math**

it is a rectangle with a height to length ratio of 2 to 25 . if the window is 24 feet high. how long is it?______ft

*February 6, 2013*

**Physics**

Well I did a similar problem but the speed was 1.5 instead of 1.6 and the answer there is 320 N/C, the proton doesnt hit the plates, the vertical displacement is 2.73*10^-6m and the displacement is downward.

*February 5, 2013*

**Organic Chemistry**

Why is the melting point of a known compound (ex. acetanilide) determined before the melting point of the unknown compound? I think it is to determine if the unknown is a pure substance but I am not sure..I just need to be pointed in the right direction.

*January 31, 2013*

**Physics**

how much heat energy needed to convert 125g ice 27 deg C to 50 deg C

*January 31, 2013*

**Math**

Chris cuts a 3 1/2 feet long board of wood. He cuts out 4 pieces that are each 2/3 foot long. Find the combined length of the 4 pieces? Find the length of the remIng board after chris gets his 4 pieces

*January 17, 2013*

**math**

A tree stands 75feet tall and cast a shadow that is 50feet long. What is the angle of elevation from where the shadow ends and the top of the tree

*January 16, 2013*

**social studies**

what are 2 unwritten practices of the roman republic?

*January 9, 2013*

**Spanish**

Im also from American hs lol but yeah its noun.

*December 13, 2012*

**Chemistry**

I am not sure if I calculated the exact molarity of the potassium permanganate. I multiplied the molarity of the potassium permanganate by the liters of potassium permanganate used in the titration and divided it by the total liters of solution. I don't know if that if how...

*November 28, 2012*

**Chemistry**

I am not sure if I calculated the exact molarity of the potassium permanganate. I multiplied the molarity of the potassium permanganate by the liters of potassium permanganate used in the titration and divided it by the total liters of solution. I don't know if that if how...

*November 28, 2012*

**Chemistry**

how do i find out what the normal boiling point of a liquid could be if the vapor pressure of the liquid is .92 atm at 60 degrees celsius?

*November 19, 2012*

**Geometry**

Help I need help to find the coordinates of the circumcenter of each triangle. Isosceles triangle CDE with vertices C(0, 6), D(0, –6), and E(12, 0)

*November 15, 2012*

**physics**

Fred the otter climbed to the top of an inclined plane. His friend, Giselle the giraffe, suggested that he was so small that gravity would ignore him and he would be unable to slide down. "On the contrary", said Fred, "Since this slope makes an angle of 48.4 ...

*November 13, 2012*

**Physics**

A mass-spring system has b/m = ω0/2, where b is the damping constant and ω0 the natural frequency. How does its amplitude A when driven at a frequency 12% above ω0 compare with its amplitude at resonance Ares at ω0?

*November 12, 2012*

**Science**

The products of the reaction between zinc and sulfuric acid are zinc sulfate, hydrogen sulfide, and water. Balance the equation using the electron-transfer method.

*November 6, 2012*

**physics**

An 8 g bullet is shot into a 4.0 kg block, at rest on a frictionless horizontal surface. The bullet remains lodged in the block. The block moves into a spring and compresses it by 7.9 cm. The force constant of the spring is 1400 N/m. What is the impulse of the block (including...

*November 6, 2012*

**chemistry**

how can we find which kinetic energy is higher?

*November 5, 2012*

**math**

How does finding the square root of a number compare to finding the cube root of a number? Use the number 64 in your explanation.

*October 31, 2012*

**Algebra**

The solution set for 6x^3-11x^2-9x-1=0

*October 30, 2012*

**Physics**

an 88kg cardboard box is being pulled along a level floor. the coefficient of static friction between the box and the floor is 0.23, and the sliding friction is 0.12. What is the weight of the box? What force is needed to start the box moving? What force is needed to keep the ...

*October 29, 2012*

**Chemistry**

I have done the calculation for this multiple times and I keep getting over 100% for the sodium carbonate in soda ash. I have no idea what I am doing wrong. I did it the way that you explained.

*October 21, 2012*

**Chemistry**

I used bromophenol blue as the indicator, and the molarity of HCl is 0.2M.

*October 21, 2012*

**Chemistry**

I titrated 0.25g of soda ash mixed with 25mL of deionized water and it took 43.7mL of hydrochloric acid to complete the titration. I am trying to figure out how to find the moles of sodium carbonate in the soda ash and then the percent of sodium carbonate in the soda ash. How ...

*October 21, 2012*

**future job**

thanks

*October 18, 2012*

**future job**

what do thet mean when they say Outlook:stable,increasing Job Openings: large number and very small number

*October 18, 2012*

**Chemistry**

I am trying to figure out how to calculate the reaction rate. In my question the reaction rate is: 1/2x molarity of sodium thiosulfate/reaction time Then I have to compare the rates of runs 1-3 and determine the orders of the reaction. Do I only find the reaction rate based ...

*October 1, 2012*

**Chemistry**

So I would multiply 3% by 20 mL which equals 0.6. Then I would divide 0.6 by 30% to get the volume of 30% hydrogen peroxide?

*September 28, 2012*

**Chemistry**

How would I find the volume of 30% hydrogen peroxide solution from 20mL of 3% hydrogen peroxide solution?

*September 28, 2012*

**chemistry**

Explain why the urea in particular, or amides in general, are much weaker bases than amines?

*September 23, 2012*

**Organic Chemistry**

Melting Point Determinations between urea and trans-cinnamic acid. Q. If urea were a significant base, specifically how would your Melting Point Diagram be different?

*September 23, 2012*

**math**

P(t) = 1000 - 19.75t + 20t² - 1/3t³, what type of function is it?

*September 16, 2012*

**Chemistry**

How would I find the percent of water lost in alum after it has dried for a week? Wet Alum = 13.44g Dry Alum = 11.28g

*September 11, 2012*

**math**

Chris has a 3 1/2 foot long board. He cuts out 4 pieces that are each 2/3 foot long. Find the combined length of the 4 pieces? Find length of the remaining board after chris gets his 4 pieces?

*September 10, 2012*

**English**

The complete subject is, Many stories about the first Valentine's day. The simple subject is stories.

*September 5, 2012*

**English**

What is the simple subject of ,Many stories about the first Valentine's Day exist?

*September 5, 2012*

**math**

one carton of juice is 10cm wide by 10 cm long. how many cartons of juice will fit on a refrigerator shelf that is 80 cm wide by 100 cm long?

*August 31, 2012*

**Chemistry**

How would I calculate the heat of solution in Joules for dissolving 0.1 mole of NH4NO3 in 100 mL of water? The initial temperature was 22.8 degrees celsius and the temperature after the salt dissolved was 18.1 degrees celsius.

*July 24, 2012*

**Chemistry**

Oh ok and I used a device called a Xplorer GLX and it measured the pressure of the flask before I put in the magnesium and hydrochloric acid and then it measured the pressure once the reaction was complete. But thank you for all of your help!

*July 15, 2012*

**Chemistry**

In the lab I had a strip of magnesium that weighed 0.029 grams and I added 15 milliliters of 0.5 M hydrochloric acid into a flask and I never used any water during the lab. So I don't really understand where I would get the water vapor pressure.

*July 15, 2012*

**Chemistry**

The reaction for my lab is Mg(s)+2HCl(aq)--> MgCl2(aq)+H2(g) I need to find the pressure of the hydrogen gas. Initial Pressure = 0.98692 atm Total Pressure = 1.64816 atm I don't know if I calculated the pressure of hydrogen gas correctly. I used the formula Total ...

*July 15, 2012*

**Chemistry**

What is the balanced equation for copper (II) sulfate pentahydrate and potassium oxalate monohydrate?

*July 6, 2012*

**Chemistry**

How would I figure out what is produced during a chemical reaction between 0.5 grams of sodium bicarbonate and 3 grams of citric acid? I know that it produces carbon dioxide and water but my professor said I am missing something from my equation.

*June 26, 2012*

**Physics**

Microwaves are electromagnetic waves transmitted at a normal frequency of 2.45 GHz. Find the wavelength of the microwaves.

*May 29, 2012*

**physics**

What is the index of refraction of a liquid in which the speed of light is 2.22 x 108 m/s?

*May 14, 2012*

**Geometry**

If you stand at stree level, the angle of elevation to a buildings tenth-story window is great than the angle of elevation to one of its ninth-story windows.

*April 24, 2012*

**Physics**

A certain dog whistle operates at 23.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 9200 Hz occurs when they are played simultaneously, estimate the operating ...

*April 23, 2012*

**Algebra**

A ball is thrown up with an initial velocity of 32 feet per second. How many seconds will it take for the ball to return to the ground using the formula h=vt-16t^2?

*March 25, 2012*

**Physics**

Block M (mass of 15.65 kg) is initially moving to the left with a speed of 3.77 m/s. The mass of m is 8.26 kg and the coefficients of friction are Us = 0.411 and Uk = 0.304. The string is massless and the pulley is massless and frictionless. How fast will M be traveling when m...

*March 1, 2012*

**physics**

A block of mass M = 6.755 kg is pulled along a horizontal frictionless surface by a rope of mass m = 0.592 kg, as shown in Fig. 5-63. A horizontal force = 41.5 N is applied to one end of the rope. Assume that the rope only sags a negligible amount. Find (a) the acceleration of...

*February 26, 2012*

**MATH**

THE RATIO OF THE PERIMETERS OF TWO SIMILAR TRIANGLES IS 1:3. htE AREA OF THE LARGER TRIANGLE IS 27FT^2. WHAT IS THE AREA OF THE SMALLER TRIANGLE. SORRY FOR THE CAPITAL LOCK. MY COMPUTER KEPBOARD WILL NOT PUT IT TO LOWER CASE SORRY AGAIN.

*February 21, 2012*

**math**

The perimeter of rectangle ABCD is 256 inches. It's length is 3 times as long as its width. Find the area of triangle ABC.

*February 14, 2012*

**Physics**

A hydraulic jack is designed so that when the handle is pushed down 1 m, the piston raising the load moves up 0.015 m. IMA= 66.67 AMA= 26.67 Efficiency= 40% At this efficiency, what is the force required to lift a 5000 N weight?

*February 9, 2012*

**physics**

When a 1150 kg space rocket lifts off of ground. How many joules of energy has been provided by its engine during the time in which it achieves a speed of 180 m/s.

*February 7, 2012*

**physics**

use s=ut + 0.5*a*t^2 in vertical direction s =0 because there is no vertical displacement at the time it reaches the ground a= -9.81 ; minus because we consider up as the positive direction. u= 24.8 sin 62.5 ; vertical component of the Velocity SO t= 2*u/ -a = (2*24.8 sin 62.5...

*January 29, 2012*

**chemistry**

yes I mean Fe2(SO4)3. How come you only used TWO of the reactants for your equation?? What happens with the third one?

*January 24, 2012*

**chemistry**

What products are formed when aqueous solutions of Na2SO4, Fe3SO42, and BaCl2 are mixed together ? Can someone help me write out a balanced equation for the reaction that occurs.

*January 24, 2012*

**Physics**

A rock (m = 1.5 kg) moving at 4.2 m/s north collides with a ball (m = 0.061 kg) that is initially at rest. What is the velocity of the rock after the collision if the velocity of the ball after the collision was 8.4 m/s north?

*January 15, 2012*

**Math (algebra)**

Matt has to bake muffins. He uses x eggs for each 200 grams of flour. If he has to use 900 grams of flour how many eggs will he use? I have to set this up as an algebra problem. I am stuck. Our class is just learning this and I don't understand.

*January 11, 2012*

**Civics**

I have a civics final tomorrw. the question I'm working on is "To Postpone Sentence/Fine" It is a crossword puzzle and the first letter is R - - - I - - - . the book says to suspend, but I can't fine any word that starts with R? Please help.

*January 10, 2012*

**vocabulary**

Thank you for the link.. I used Gloom is the prevailing mood after we lost the basketball game.

*January 10, 2012*

**vocabulary**

How do I use the word prevailing in a sentence?

*January 10, 2012*

**Physics**

A 34-g bullet traveling at 120m/s embeds itself in a wooden block on a smooth surface. The block then slides toward a spring and collides with it. The block compresses the spring (k=100 N/m) a maximum of 1.25 cm. Calculate the mass of the block of wood.

*January 5, 2012*

**Physics**

A 200 g mass is attached to a spring of spring constant k. The spring is compressed 15 cm from its equilibrium value. When released the mass reaches a speed of 5 m/s. What is the spring constant (in N/m)?

*January 5, 2012*

**Physics**

A ball bounces upward from the ground with a speed of 14 m/s and hits a wall with a speed of 12 m/s. How high above the ground does the ball hit the wall? Ignore air resistance.

*January 5, 2012*

**Chemistry**

A(n) ____ reaction is one in which oxygen reacts with another compound to form carbon dioxide, water, and heat.

*January 4, 2012*

**french**

I am supposed to choose from pronom indirect (indirect pronouns), and pronom disjoint (stressed pronuons). Naturally, if you had an answer for the question, you'd know what those meant, but I just thought I should give a better idea of my level of understanding... Anyway, ...

*December 18, 2011*

**8th Grade**

301 m

*December 5, 2011*

**Physics**

A 10-g bullet is shot vertically into a stationary 8-kg block. The block lifts upward 3.0 mm. The bullet penetrates the block in a time of .001 seconds. Assume the force exerted on the block is constant. What is the impulse imparted on the block by the bullet?

*November 30, 2011*

**Algebra II**

The intensity of illumination at a given point is directly proportional to the intensity of the light source and inversely proportional to the square of the distance from the light source. If a desk is properly illuminated by a 74.0 w lamp 8.00 ft from the desk, what size lamp...

*November 21, 2011*

**Algebra II**

The volume of a given weight of gas varies directly as its absolute temperature t and inversely as its pressure p. If the volume is 4.45 m^3 when p=225 kilo pascals (kpa) and t = 305 K, find the volumn when p = 325 kpa and t = 354 k.

*November 21, 2011*

**Algebra II**

The amount paid to a work crew varies jointly as the number of persons working and the length of time worked. If 5 workers earn $5123.73 in 3.0 weeks, in how many weeks will 6 workers earn a total of $6148.48?

*November 21, 2011*