Derek adds water to a pool at a rate of 12 gallons per minute and then reduces the rate to to 8 gallons per minute. Derek adds water to pool for a total of 2 hours. Let t be the time in hours that he adds water to the pool at the faster rate. Write an algebraic expression to represent how many minutes he adds water to the pool at each rate.

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Answer:

At the faster rate (12 gallons per minute)

Time = 60t minutes

At the slower rate (8 gallons per minute)

Time = 120 - 60t minute

Step-by-step explanation:

From the question,

  • Derek adds water to a pool at a rate of 12 gallons per minute and then reduces the rate to 8 gallons per minute.

From the statement above, it means 12 gallons per minute is the faster rate and

8 gallons per minute is the slower rate

Also,

He adds water to the pool for a total of 2 hours. That is, the total time he spends adding water to the pool at both rates is 2 hours.

From the question, let t be the time in hours that he adds water to the pool at the faster rate. That is,

At the rate of 12 gallons/minute

Time = t hours (Convert to minute)

(NOTE: 1hour = 60 minute)

Time = t × 60 minute

Time = 60t minute

Since the total time spent was 2 hours, then

The time spent when adding water at the rate of 8 gallons / minute will be

Time = 2 - t hours (convert to minute)

Time = (2 - t) × 60 minutes

Time = 120 - 60t minutes

Hence, the algebraic expression for the time he spends adding water to the pool at the faster rate is

Time = 60t minutes

and for the slower rate

Time = 120 - 60t minute