Question

Plz answer fast................


I'll surely mark as brainliest....

Answer 1

Answer:

3(3/5) hours (or) 3 hours 36 minutes

Step-by-step explanation:

(i) Amount of work done by A in 1-hour = (1/6).

(ii) Amount of work done by B in 1-hour = (1/4).

Total work done by (A + B) in 1-hour = (1/6 + 1/4) = 10/24 = 5/12.

Given that After first has worked for 2 hours, he is joined by other.

A's 2-hours work = 2 * (1/6) = 1/3.

Remaining work = 1 - (1/3) = 2/3.

Now,

(5/12) of the work is done by (A + B) in 1-hour.

Then, (2/3) of the work is done by (A + B) in :

= (2/3) * (12/5)

= 24/15

= 8/5 hours

But, it is given that A has worked already for 2 hours.So,

= 2 + (8/5)

= 18/5 hours

= 3 (3/5) hours (or) 3 hours 36 minutes.

Therefore, Work should be completed in 3(3/5) hours (or) 3 hours 36 mins

Hope it helps!

Answer 2

Answer:

8/5 hour or 1.6 hour

Step-by-step explanation:

Given:

2 men can do a piece of work in 6 hours and 4 hours respectively .

Now,

First man worked for 2 hours .
Then, the other man joined .

In Conclusion:

First man complete it in 6 hours .
∴ In 1 hour he does 1/6 part of the work .

In 2 hours, he does 1/3 part of work.

∴ 1 - 1/3
⇒ 2- 1/3
⇒ 1/3 part is left

Again,
Both will do the work .

Both can do :
⇒ 1/4 + 1/6
⇒ ( 3 + 2 )/12
⇒ 5/12 part of work in 1 hour

Let the time be k .

∴ 5/12 × k = 2/3
⇒ 5k / 12 = 2 / 3
⇒ 5k = 2 × 4
⇒ k = 8/5 hours

By Dividing 8/5 hours:

⇒ 1.6 hours
⇒ 1 hour 60 minutes

Hence, The work should be completed in 1 hour 60 minutes.