The farm where you just started working has a vertical cylindrical oil tank that is 2.5 feet across on the inside. The depth of the oil in the tank is 2 feet. If 1 cubic foot of space holds 7.48 gallons, about how many gallons of oil are left in the tank?
Answer to Level 7 Sample Item
First, look up the formula for the volume of a cylinder (π r 2h). Next, divide the diameter
(2.5 ft) by 2 to find the radius (1.25 ft) and calculate the volume of the cylinder (9.81 cu ft). Finally, the volume must be multiplied by 7.48, the number of gallons per cubic foot, to find the number of gallons remaining in the tank.
- Multiplied 2.5 x 2 x 7.48 = 37.4, then rounded down to 37
- Forgot to square 1.25; 3.14 x 1.25 x 2 x 7.48 = 58.72, then rounded up to 59
- 2.5 ÷ 2 = 1.25; 3.14 x (1.25)2 x 2 = 9.81 cu ft; 9.81 cu ft x 7.48 gal/cu ft = 73.4 gallons, then rounded down to 73
Correct
- (1.25 x 3.14)2 x 2 x 7.48 = 230.47, then rounded down to 230
- 3.14 x (2.5)2 x 2 x 7.48 gal/cu ft = 293.59 gallons, then rounded up to 294: Used diameter2 instead of the radius
