How many gallons of water will be in the pool at 2pm if at 11am there was 300 gallons and 12pm there was 600 gallons

Question

At 10 am Gary started filling up his 10,000 gallon pool. At 11 am he had 300 gallons, at 12 pm he had 600 gallons and at 1pm he had 900 gallons. How much will he have in the pool by 2pm?

Answer 1

Hi Nicole!

 

Thanks for posting. To answer this, you need to figure out how fast Gary's filling the pool. We'll call this the rate.

 

Think of 10am as "Hour Zero" (the start time). By 11am, one hour later, he has 300 gallons. So, he filled 300 gallons in 1 hour. Let's see if 300gal/hr (gallons per hour) holds steady. That would mean after another hour (at noon) he'd have 300 + 300 = 600 gallons. That's true! So, we can write this:

 

total amount of water = 300 gallons x number of hours since 10am. I'm writing it like this because 10am is the "zero hour."

 

I'm going to shorten this equation: a = 300h. A stands for amount, and h stands for hours.

 

Now, how long after 10am is 2pm? 4 hours. So, let's put it into the equation.

 

a = 300*4 = 1200 gallons.

 

To check our work, let's see if the amount at 1pm plus 300 gallons equals the amount at 2pm. 900 + 300 = 1200.

 

So, we know 1200 gallons is right.

Answer 2

Well, it's obvious that it's 300 gallons/hour, so after one more hour, there will be 1200 gallons.

 

The algebraic way...

 

(600 - 300)/(12 - 11) = 300 gallons/hour

 

Since it's one hour from 1 to 2, 900 + 300 = 1200