Question

2 men can build a wall in 9 hrs and 10 hrs respec-

tively. But if they work together then they use 10

less bricks per hours and build a wall in 5 hrs. Then

find the no. of bricks to build the wall?​

Answer 1

it will be useful for you

Answer 2

900 bricks are required to build the wall.

Let us assume that there are in total x bricks.

Given the first man 'A' takes 9 hour to build a wall.

So 'A' 's work done per hour is (1/9).

So, bricks taken by A = x/9 per hour.

Similarly, the second man 'B' takes 10 hours to build a wall.

So 'B' 's work done per hour is (1/10).

So, bricks taken by B = x/10 per hour.

Thus, according to question, A will use x/9 bricks per hour and B will use x/10 bricks per hour.

Now when they work together, they take 10 bricks less, so the number of bricks per hour used by them will be (x/9 + x/10 – 10) and the work is done in 5hrs. So,

[(x/9 + x/10 – 10) × 5] = x.

⇒x/9 + x/10 - 10 = x/5

⇒x/9 + x/10 - x/5 = 10

⇒ 50x + 45x - 90x = 10 × (9×10×5)            [Multiplying both sides by (9×10×5)]

⇒5x = 10 × (9×10×5)  

⇒ x = 10 × 9 × 10 = 900

Total bricks are 900.