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?

at 10 hours  there will be 10 * 5 = 50 gallons

at 15 hours there will be 50 +5*5 -2*5 gallons = 65 gallons   (25 added by the hose and 10 lost to the animals)

at 15 hours we add another hose so our input rate is 9 gallons per hour and our output rate is 2 gallons per hour = net input is 7 gallons per hour

we need 100 gallons in the pool and we have 65 gallons at 15 hours so we still need 35 gallons

35/7 =5

so 5 more hours

15 +5 = 20 hours

At 20 hours the pool will be full.

both equations and proportions are better.

there is no grid

step-by-step explanation: