Multiple choice

There are two concentric circles with circumferences 40 cm and 98 cm. Find the approximate area between them.

  1. 367 cm2

  2. 432 cm2

  3. 637 cm2

  4. 535 cm2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Circumference 1 = 40, r1 = 40/(2*pi) = 6.366. Circumference 2 = 98, r2 = 98/(2*pi) = 15.597. Area = pi * (r2^2 - r1^2) = pi * (15.597^2 - 6.366^2) = pi * (243.27 - 40.53) = pi * 202.74 = 637.05.

AI explanation

Using the circumference formula, the radii of the circles are 40 over two pi and 98 over two pi, which approximately equal 6.37 cm and 15.60 cm. The area between the circles is found by subtracting the area of the smaller circle from the larger circle using pi times the difference of their squared radii. Calculating 22 over 7 times 15.60 squared minus 6.37 squared gives approximately 637 square cm.

Keep practicing — related questions