Question

I have a question:-
A certain piece of work can be completed in 9 days by 420
men.How many more men are required to complete the work in 7 days

Answer 1

Answer: 120 men need

Step-by-step explanation:

need = total-420

1 men=1/(420*9)

men=(9*420/7)

      =540

needed=540-420

            =120 men

Answer 2

Given: 420 men can complete a work in 9 days

To find: How many more men are required to complete the work in 7 days

Let: The number of men required to complete the work in 7 days be $x$

Solution: According to the given question and assumption made:

420 men can do the work in 9 days and

$x$ men can do the work in 7 days

For finishing the work in less number of days, more men will be required.

So, this is a case of inverse proportion.

∴ $420 * 9 = x * 7$

⇒ $7x = 3780$

⇒ $x = \frac{3780}{7} = 540$

So, 540 men can finish the work in 7 days.

Now, 540 - 420 = 120

Hence, 120 more men are required to complete the work in 7 days.