12 men complete a work in 9 days. After they have worked for 6 days, 6 more men join them. How many days will they take to complete the remaining work?

Question: 12 men complete a work in 9 days. After they have worked for 6 days, 6 more men join them. How many days will they take to complete the remaining work?

Solution:
12 men's 9 day's work 1 part
12 man's 1 day's work 1/9 part
12 men's 6 day's work 6/9 part
= 2/3 part

Remaining work = 1 - 2/3 = 1/3 part

After 6 men joined, total men = 12 + 6 = 18

Again,
12 men can do 1 part of the work in 9 days
1 man can do 1 part of the work in 9 × 12 days
18 men can do 1/3 part of the work in (9 × 12)/(18 × 3) days
= 2 days