The volume of a cone is 88π cubic feet. Its height is 8 feet. Fatima is finding the radius of the cone. Her work is shown below.

Step 1: 88π = 1/3 πr² (8)

Step 2: 88π = 8/3 πr²

Step 3: 8/3 (88) = r²

Step 4: 234.7 = r²

Step 5: 15.3 = r

What is Fatima's error?

- In step 4, Fatima did not find the correct value of 8/3 (88).

- In step 2, Fatima should not have multiplied 1/3 and 8.

- In step 3, Fatima did not multiply 88 by the reciprocal of 8/3

- In step 1, Fatima did not substitute the correct value for the height in the formula.

Question

Mathematics

Lilly Dawson

4 May, 17:52

The volume of a cone is 88π cubic feet. Its height is 8 feet. Fatima is finding the radius of the cone. Her work is shown below.

Step 1: 88π = 1/3 πr² (8)

Step 2: 88π = 8/3 πr²

Step 3: 8/3 (88) = r²

Step 4: 234.7 = r²

Step 5: 15.3 = r

What is Fatima's error?

- In step 4, Fatima did not find the correct value of 8/3 (88).

- In step 2, Fatima should not have multiplied 1/3 and 8.

- In step 3, Fatima did not multiply 88 by the reciprocal of 8/3

- In step 1, Fatima did not substitute the correct value for the height in the formula.

+3

Answers (1)

Know the Answer?

Marshall Drake · Answer 1

To evaluate the radius of the cone we proceed as follows:

V=1/3 πr²h

plugging in the values, v=88π, h=8 ft

step 1

88π1/3πr² (8)

step 2

88π=8/3πr²

step 3

divide both sides by π

88=8/3r²

multiply both sides by 3 / (8)

88 (3/8) = r²

step 4

simplify

33=r²

step 5

get the square root

r=√33

Thus the mistake that Fatima made was:

In step 3, Fatima did not multiply 88 by the reciprocal of 8/3