IMPORTANT CONCEPT: After 8 hours, 3/5 of the job is finished and 2/5 of the job is remaining.
This means the remaining part of the job is 2/3 the size of the first part of the job.

Think of it this way:
If the pool had a capacity of 5 gallons, then the first part of the job would be filling 3 gallons, and the remaining part of the job is filling 2 gallons.
So, the remaining part of the job (filling 2 gallons) is 2/3 the size of the first part of the job (filling 3 gallons)

So, if it takes 8 hours to do the first part of the job, then the time to do the remaining part = 2/3 of 8 hours
2/3 of 8 hours = 2/3 x 8 hours
= 16/3 hours
= 5 1/3 hours
= 5 hours 20 minutes

Answer: B

Cheers,
Brent

it takes 8h to fill 3/5
i look for how long it would take to fill entirely the pool - simple cross calculation.

8 x 1 hour = (time for full pool) x (3/5)

time for full pool = (8 x 1 hour) / (3/5)
time for full pool = 8/(3/5)
time for full pool = 8*(5/3) = 40/3 hours

to calculate the time remaining to complete the job, i remove the 8h

40/3 - 8 = (40-24)/3 = 16/3 = 5 hours and 1/3 or 5h20min

answer B

Work-----------------------------------Time
3/5-------------------------------------8 hours
2/5(Remaining work(1-3/5))---------x hours

More time more work, less time less work so its a directly proportional relationship, hence we will cross multiply
3/5x = 2/5(8)
x=5 1/3 hours (dont go for option A, its a trap)
convert 1/3 into min by multiplying by 60 so 1/3*60 = 20 min
so 5 hours 20 mins option B

We can solve it without using any formula!

Let us assume that the tank is divided into 5 equal parts, each having X capacity
So the total tank capacity is 5X

Now, If 3 parts are being filled in 8 hours, so on average each part takes 8/3 hours to fill
3X = 8 i.e. X= 8/3

So, the Leftover capacity (2X) can be filled in 2 x (8/3) = 16/3 hours = 5.33 hours = 5 hours 20 minutes

Hence, option B

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