A can do 20% of a job in 7 days and B can do 25% of the job in 7 days if they worked alone. How much of the job (in percentage) can they complete in 7 days if they worked together?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 45%.
Given:
A can do 20% of a job in 7 days
A alone can do whole job in = 7 × 5 = 35 days
B can do 25% of the job in 7 days
B alone can do whole job in = 7 × 4 = 28 days
Calculations:
Total work (LCM 35, 28) = 140 units
The efficiency of A = 140/35 = 4
The efficiency of B = 140/28 = 5
Work done in 7 days by A and B = 7 × (5 + 4) = 63 units
Hence, The required percentage = (63/140) × 100 = 45%