I need a simple way to solve this question.

It takes 3 men to gig 2 identical trenches in 5 hours .If all the men work at the same rate ,how long will it take 5 men to dig 7 of these trenches ?

i have solved it this way through the help of an example in the book.

Solution

First we keep the number of trenches constant

No of men --- No of trenches --- No of Hours

3 --- 2 --- 5

1 --- 2 --- 5*3

5 --- 2 --- (5*3)/5=3

Next we keep the number of men constant

No of men --- No of trenches --- No of Hours

5 --- 2 --- 3

5 --- 1 --- 3/2=1.5

5 --- 7 --- 1.5*7=10.5

Therefore 5 men will take 10.5 hours to dig 7 identical trenches.

I want a simpler solution to this.