Old McDonald purchased a pool with a capacity 100 gallons for his farm. One day, at 1:00 p.m., he placed a hose onto the pool which filled it with water at a rate of 5 gal per hour. After 10 hours, horses and cows started drinking the water at a rate of 2 gal/hr. Five hours after that, Mr. McDonald noticed the animals and placed a second hose in the pool which filled it at a rate of 4 gal/hr. When did Mr. McDonald have himself a pool full of water?

If the animals drank 2 gal/h with it still being filled at 5 gal/h FOR 5 HOURS, you subtract the 25 (5 gal/h times 5 hours) by 10 (2 gal/h times 5 hours) to get how much gallons were filled in that time span, which is 15

Since he added a hose that filled at 4 gal/h, you can infer that, in total, it is now 9 gal/h because you add 5+4.

The animals are still going to drink at 2 gal/h, so you subtract 9 from 2 and get 7 gallons filling up the pool per hour.

Since you have 35 gallons left (you already filled 65 gallons), you can divide the 35 by 7 to get 5 hours.

fichoh fichoh · Answer 2 · 2021-10-26T16:13:48+02:00

Based on the fill rate, discharge rate and time given, the pond should be filled up by 9:00 a.m the next morning.

Pool capacity = 100 gallons

Initial filling rate = 5 gallons per hour

Amount of water in pool after 10 hours:

Filling rate × time

Amount of water in pool after 10 hours = 5 × 10 = 50 gallons

Discharge rate after 10 hours = 2 gallons per hour

Net filling rate = 5 gal/hr - 2gal/hr = 3 gal/hr

Amount of water filled into the po at this rate after 5 hours :

3 gal/hr × 5 hr = 15 gallons

Additional recharge = 4 gal/ hr

Net filling rate = 3gal/hr + 4 gal/hr = 7 gal/hr

Amount of Gallons left = 100 - (50 + 15) = 35 gallons

Number of hours till full = (gallons left) ÷ fill rate

Number of hours left = (35 ÷ 7) = 5 hours

Hence, the pool will be full after (10 + 5 + 5) = 20 hours

Therefore, the pond will be full at 9:00 am the next day.

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