Question

Aman can complete a work in 30 days. If the efficiency of Aman is twice the efficiency of Parul and the efficiency of Parul is thrice the efficiency of Charu, find how many days will be taken to complete the work by all working together. 
1. 20 
2. 18
3. 17
4. 16

Answer 1

Correct Answer - Option 2 : 18

Given 

Aman can do work = 30 days 

Formula Used 

Work = time × efficiency 

Calculation

Let the efficiency of Aman, Parul and Charu be A, P and C respectively 

⇒ A : P = 2 : 1 

⇒ P : C = 3 : 1 

⇒ A : P : C = 6 : 3 : 1 

⇒ So, total work = 6x × 30 = 180x 

⇒ Now, calculate number of days to complete the work when they work all together 

⇒ Total efficiency = 10x 

⇒ No. of days = total work/ total efficiency 

⇒ 180x/10x = 18 days 

∴ 18 days is required to complete the work when they work all together.