Assume that it takes an average of 3 man-hours to stack 1 ton of a particular item. In order to stack 36 tons in 6 hours, the number of people required is:. A) 9
B) 12
C) 15
D) 18
E) 21

option (d)

Explanation:

Given,

1 ton of a particular item can be stack in= 3 man-hours

36 ton of a particular item can be stack in=  36 x 3 man-hours

                                                                     = 108man- hours

Number of hours = 6 hours

Number of people =

                               = 18

Hence, the number of people required is 18.

Therefore, option (d) is correct.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.