Question

20 men can do a piece of work in 18 days. They worked together for 3 days, then 5 men joined then. In how many more days is the work completed? 

(a) 12 days 

(b) 14 days 

(c) 13 days 

(d) 15 days

Answer 1

Correct option (a) 12 days

Explanation: 

20 → 18 days 

⇒Work done by 20 men working together = 1 work 

⇒Work done by them in 3 days working together = 1×3=3 work 

⇒Remaining work =18-3=15 work 

⇒15 work is to be done by (20+5)=25 men 

∴ Efficiency of 20 men= 1 

Efficiency of 1 men = 1/20

Therefore, 12 more days will be taken to finish the remaining work

Alternate:- 20 men can do 18 days 

So total work = 18×20 =360 

20 men 3 days work = 20×3 =60 

Remaining work = 360-60=300 

After joining 5 men total men = 20+5

so 300/25 = 12 days