Correct Answer - Option 3 : 60/7
Given :
A can do a work in ‘x’ days
B can do the work in 15 days
The efficiency of ‘A’ is 75% of the efficiency of ‘B’
Concept used :
The efficiency of a person × Number of days he took to complete the work = Total Work
Number of days to complete the work = Total work/Work done every day
Calculations:
Let the working efficiency of B be ‘b’
Let the working efficiency of A be ‘a’
Work for A = Work for B
The efficiency of A × x = Efficiency of B × 15
⇒ a × x = b × 15
⇒ 75% of b × x = b × 15
⇒ (3/4) b × x = b × 15
⇒ x = 20 days
Now, total work = LCM of 20 and 15 = 60 units
A’s per day work = (Total work/Total days he took) = 60/20
⇒ 3 units
B’s per day work = 60/15
⇒ 4 units
A and B total work for everyday = 4 + 3 = 7 units
Total number of days taken by them = Total work/work done by them every day
⇒ 60/7
∴ They both will complete the work in 60/7 days
