Seven pipes empty a water tank in five days. In how many days would four pipes empty this tank? Give your answer in days and hours.

It would take 8 days 18 hours for 4 pipes to empty the tank.

Step-by-step explanation:

To solve this, first, we need to check if this is a direct or indirect proportion

As the number of pipes increases, the number of days to empty a water tank decreases, as the number of pipes decreases, the number of days it takes to empty a water tank increases. This is an indirect proportion.

Solving using  proportion;

since it is an indirect proportion, the arrangement differs from that of the direct proportion, it will be arrange inversely to each other

Let x be the number of days it will take to empty 4 pipes

7 pipes = 4 pipes

 x         = 5 days

cross-multiply

4×x = 7×5

4x = 35

Divide both-side of the equation by 4

4x/4 = 35/4

x = 8.75 days

But we are asked to leave our answer in days and hour

8.75 days = 8 days + 0.75 days

0.75 day is not up to a day, so we will change it to hour

0.75 day = 0.75 × 24 hours =  18 hours

8.75 days = 8 days 18 hours.

Therefore, it would take 8 days 18 hours for 4 pipes to empty the tank.