A machine puts c caps on bottles in m minutes. How many hours will it take to put caps on b bottles?
A. 60bm/c
B. bm/60c
C. bc/60m
D. 60b/cm
E. b/60cm
Here is a good example of a question that is made easier by substituting values for the variables. Let’s say the machine puts on 10 caps (so c=10) every minute (so m=1). What would the equivalent of that be in hours? If it puts on 10 caps per minute, then it will put on 10 X 60 caps per hour. Putting that back into the original variable form, the number of caps per minute is c/m; the number per hour is (c x 60)/m, or 60c/m. Now the question is how many hours it will take to put caps on b bottles. The rate per hour is 60c/m. We need to divide the total number of bottles (b) by the rate (60c/m).
With that we get b/(60c/m). Remember that when you have a fraction in which the denominator contains a fraction, you can multiply the numerator by the reciprocal of the denominator. For example, 1 divided by 2/3 is the same thing as 1 multiplied by 3/2. Here, b divided by 60c/m is the same as b multiplied by m/60c, or bm/60c. The answer is (B).
source: majortests.com
