Find Circumferences and Areas of Circles Using a Calculator Worksheet

This worksheet is about finding the circumferences and areas of circles using a calculator.

You must learn the two important formulae below to find the radius of a circle (r)

Circumference of a circle = 2 π r

Area of a circle = π r²

Examples

Find the circumference and area of a circle of radius 6 cm.

Answers

Circumference = 2 π r = 2 x π x 6 = 12 x π = 37.7 cm (1 dp)

Area = π r² = π x 6² = π x 36 = 113.1 cm² (1 dp)

Find the circumference of a circle of radius 25 cm.

(Give your answer to 1 decimal place)

Find the circumference of a circle of radius 26 cm.

(Give your answer to 1 decimal place)

Find the circumference of a circle of radius 71 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of radius 16 cm.

(Just write the number to 1 decimal place)

Find the circumference of a circle of radius 57 cm.

(Just write the number to 1 decimal place)

Find the area of a circle of radius 41 cm.

(Just write the number to the nearest whole number)

Find the area of a circle of radius 31 cm.

(Just write the number to the nearest whole number)

Find the area of a circle of radius 4 cm.

(Just write the number to the nearest whole number)

Find the area of a circle of radius 43 cm.

(Just write the number to the nearest whole number)

Find the area of a circle of radius 13 cm.

(Just write the number to the nearest whole number)

ANSWERS

Question 1

Find the circumference of a circle of radius 25 cm.

(Give your answer to 1 decimal place)

CORRECT ANSWER

157.1

EDDIE SAYS

To calculate the radius we know that our calculation is 2 x π x r 2 x π x 25 = 157.07963.. To one decimal place this becomes 157.1- always check what decimal place the question asks you to give.

ANSWERS

Question 2

Find the circumference of a circle of radius 26 cm.

(Give your answer to 1 decimal place)

CORRECT ANSWER

163.4

EDDIE SAYS

2 x π x 26 = 163.362817... To one decimal place, this gives us 163.4

ANSWERS

Question 3

Find the circumference of a circle of radius 71 cm.

(Just write the number to 1 decimal place)

CORRECT ANSWER

446.1

ANSWERS

Question 4

Find the circumference of a circle of radius 16 cm.

(Just write the number to 1 decimal place)

CORRECT ANSWER

100.5

ANSWERS

Question 5

Find the circumference of a circle of radius 57 cm.

(Just write the number to 1 decimal place)

CORRECT ANSWER

358.1

ANSWERS

Question 6

Find the area of a circle of radius 41 cm.

(Just write the number to the nearest whole number)

CORRECT ANSWER

5281

EDDIE SAYS

Area = π x r² π x 41² = 5281.0172... To the nearest whole number, we would write 5281. Don't worry if you got caught out and gave your answer to one decimal point instead- this is how you learn!

ANSWERS

Question 7

Find the area of a circle of radius 31 cm.

(Just write the number to the nearest whole number)

CORRECT ANSWER

3019

EDDIE SAYS

We know that area = π x r² π x 31² = 3019.070... Be careful, this question asks that we give our number to the nearest whole number. So, we needed to write 3019.