Question

2 men can build a wall in 15 and 20 hours respectively but if they work together they use 280 less bricks per hour and build a wall in 12 hours. Find the number of bricks in the wall.​

Answer 1

Answer:

i cant understand it plz check it

Answer 2

Answer:

8400

Step-by-step explanation:

Let the total work = 1

A 's one hour work = 1/15

B's one hour work = 1/20

Together one hour work = 1/20 + 1/15

= 7/60

If they use 280 less bricks per hour and build a wall in 12 hours,

their one hour work = 1/12

Now,

Let the total no. of bricks be ' x '

In the first case, bricks used in per hour = 7x/60

In the second case, bricks used per hour = x/12

Now the difference in these rates is given as 280

=> 7x/60 - x/12 = 280

=>( 7x - 5x)/60 = 280

=> x/30 = 280

=> x = 8400