For a pool measuring 20 feet by 40 feet, with a slope from 3 feet to 7 feet, how many gallons of water does it approximately hold?

To determine the approximate volume of water a pool holds, we can start by calculating the average depth based on the depth range provided. In this case, the pool slopes from 3 feet at one end to 7 feet at the other end. We find the average depth by adding the two depths and dividing by 2:

(3 feet + 7 feet) / 2 = 5 feet average depth.

Now, we can calculate the volume in cubic feet by multiplying the surface area of the pool by the average depth. The surface area of the pool can be calculated by multiplying its length and width:

20 feet * 40 feet = 800 square feet.

Now, multiply the surface area by the average depth to find the volume in cubic feet:

800 square feet * 5 feet = 4,000 cubic feet.

Next, to convert cubic feet to gallons (since there are 7.48 gallons in a cubic foot), we multiply the volume in cubic feet by 7.48:

4,000 cubic feet * 7.48 gallons/cubic foot = approximately 29,920 gallons.

Rounding this number gives us about 30,000 gallons. Therefore, the calculation aligns with the choice of approximately 30,