Astudent charges twenty dollars per hour to type college papers. the student's average typing speed is fifty words per minute. at this rate, how much should the student charge for typing a paper that contains 31,500 words?
a) $175
b) $195
c) $210
d) $230

The student should charge $210 for typing the paper ⇒ answer C

Step-by-step explanation:

* Lets explain how to solve the problem

- The rate of the student's typing is 50 words per minute

- The students charges twenty dollars per hour to type the college

 papers

- There is a paper contains 31,500 words

- We want to now how much the student should charge for it

* At first lets find his rate per hour

∵ 1 hour = 60 minutes

∴ 1 minute = 1/60 hours

∵ His rate = 50 words / 1 minute

- Lets change the minute to hour

∴ His rate = 50/(1 × 1/60) = 3000 words per hour

* Lets find the time he needs to finish the paper

∵ The paper contains 31,500 words

∵ Time = The number of words ÷ his rate of typing

∵ his rate is 3000 words per hour

∴ Time = 31,500 ÷ 3000 = 10.5 hours

∴ He needs 10.5 hours to finish the paper

∵ He charges $20 per hour

∵ The time to finish the paper is 10.5 hours

∵ The price of typing the paper = the charge per hour × number

   of hours

∴ The price of typing the paper = 20 × 10.5 = 210

∴ The student should charge $210 for typing the paper

- "runner b is moving at a slower rate."

- "the graphs shown are graphs of distance(km) against time(min).

the slopes of this graphs are are given by:

slope = (change in y)/(change in x)

= (change in distance)/(change in time)

this is the formula for finding the speed. so, the slope of these graphs represent the speed of the runner.

taking each division in the graph to represent 1 on both axis:

runner a ⇒ speed = (2-0)/(1-0)

= 2/1

= 2 km/min

runner b ⇒ speed = (3-0)/(3-0)

= 3/3

= 1 km/min

this shows that   runner b is moving at a slower rate."