# math

a person can copy the final exam in 28 minutes using a new copy machine. using an old copy machine, it takes 70 minutes. if both machines are used, how long will it take to complete the job

1. 👍
2. 👎
3. 👁
1. 1/b = 1/28 + 1/70
b = ?

1. 👍
2. 👎
2. 2.5

1. 👍
2. 👎

## Similar Questions

1. ### Pre-Algebra

Two similar triangles have a scale factor of 5/3. a) Find the perimeter ratio copy/original b) Find the area ratio copy/original

2. ### Algebra

Explain why you think a sign on a copy machine reading ".05 (cent sign) a copy" is put up by mistake?

3. ### statistics

At a local manufacturing plant, employees must complete new machine set ups within 30 minutes. New machine set-up times can be described by a normal model with a mean of 22 minutes and a standard deviation of four minutes. a. What

4. ### Math

a photocopy store advertises the following prices: 5 cents per copy for the first 20 copies, 4 cents per copy for the 21st through 100th copy, and 3 cents per copy after the 100th copy. Let x be the # of copies, and let y = the

1. ### Math

The time needed to complete a final examination in a particular college course is normally distributed with a mean of 83 minutes and a standard deviation of 13 minutes. Answer the following questions. What is the probability of

2. ### Math

Charles is renting a large copy machine for his company and has been given a budget of ​\$1127. The machine he wants to rent will require a ​\$223 installation fee and a ​\$113​-per-month rental contract. How many months will

3. ### general

Which of the following would you use to sort through slides for a slide presentation? a. camera b. opaque projector c. copy machine d. light box

4. ### Algebra

One copy machine can run off copies in 170 minutes. A newer machine can do the same job in 119 minutes. How long does it take the two​ machines, working​ together, to make all of the necessary​ copies?

1. ### Geometry

In geometry, a common standard setting for enlarging on a copy machine is 121 percent. What does this mean?

2. ### Statistics

At a local manufacturing plant, employees must complete new machine set ups within 30 minutes. New machine set-up times can be described by a normal model with a mean of 22 minutes and a standard deviation of four minutes. b. The

3. ### math

the officejet printer can copy Janet's dissertation in 10 minutes. The laserjet printer can print the same copy in 20 minutes. If the two machines work together, how long would they take to copy the dissertation?

4. ### Math

A copy machine makes 60 copies per minute. A second copy machine makes 80 copies per minute. The second machine starts making copies 2 minutes after the first machine starts. Both machines stop making copies 8 minutes after the