Question

The efficiency of A is 40% more than the efficiency of B. A takes 30 days to complete a work. B started the work alone and then A joined B 5 days before the completion of the work. For how many days B worked alone? 
1. 25 days
2. 28 days
3. 30 days
4. 35 days

Answer 1

Correct Answer - Option 3 : 30 days

Given:

Efficiency of A = 40% more than efficiency of B

Time taken by A = 30 days

Formula Used:

Work = Efficiency × Time

Calculation:

Let the efficiency of B = 10 units

Hence, A's efficiency = 14 units

Hence, A's total work = 30 × 14 = 420 units

If B worked alone for 'n' days, we get:

(10 × n) + (10 + 14) × 5 = 420

⇒ 10n = 420 - 120 = 300

⇒ n = 300/10 = 30 days  

∴ B worked alone for 30 days