smartyman wrote:

If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61

B. 64

C. 84

D. 81

E. 94

Please help explains using rates formulae as I could not get the answer. Thanks

One version of the rate formula approach . . .

Use standard W = RT formula, but add (# of workers or machines) to R*T, thus: W =

#*R*T

Work = (# of workers) * individual rate * timeScenario 1Get individual rate from first scenario, where t = (30 * 9hrs = 270 hrs)

Work = # * r * t1 = 6 *

?? * 270

1 =

r * 1620

r =

\(\frac{1}{1620}\)Scenario 2At that rate, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

t = (25 * 8 hrs = 200 hrs)

Work = # * r * t 10 =

?? *

\(\frac{1}{1620}\) * 200

10 =

# *

\(\frac{200}{1620}\)# of workers =

\(\frac{10}{(\frac{200}{1620})} =\) # of workers =

\((10 * \frac{1620}{200})=(\frac{1620}{20})=\frac{162}{2}= 81\)Answer D

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