Seven girls can do a piece of work in 13 days, six boys can do the same piece…
2022
Seven girls can do a piece of work in 13 days, six boys can do the same piece of work in 12 days, nine men can do the same piece of work in 9 days and six women can do the same piece of work in 14 days. Who are the most efficient?
Answer: A. Boys — ConceptEfficiency means work done per person per day, not the number of days a whole group takes. If a group of N people finishes one unit of work in D days,…
- A.
Boys
- B.
Girls
- C.
Women
- D.
Men
Attempted by 15 students.
Show answer & explanation
Correct answer: A
Concept
Efficiency means work done per person per day, not the number of days a whole group takes. If a group of N people finishes one unit of work in D days, the team's combined person-days is N x D, and each individual's daily rate is 1 / (N x D). The smaller the value of N x D, the higher the individual efficiency.
Applying it to each group
Girls: N x D = 7 x 13 = 91, so each girl's rate = 1/91 per day.
Boys: N x D = 6 x 12 = 72, so each boy's rate = 1/72 per day.
Men: N x D = 9 x 9 = 81, so each man's rate = 1/81 per day.
Women: N x D = 6 x 14 = 84, so each woman's rate = 1/84 per day.
Cross-check
Cross-check: compare the person-day totals 91, 72, 81 and 84. The smallest total is 72, which gives the largest individual daily rate 1/72. Hence one boy does more work per day than one girl, one man or one woman, so boys are the most efficient.