Let’s solve each problem one by one, step by step.
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Problem 1:
We are given a circle with radius =
4 cm.
Formula for area of a circle:
> A = πr²
Plug in r = 4:
A = π × (4)² = π × 16 =
16π cm²
Check the options:
A) 8π → too small
B) 4π → way too small
C) 16π → matches!
D) 64π → that would be if we did 4³ or something — no.
✔ So, correct answer is
C
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Problem 2:
Circle with radius =
9 in
Use same formula: A = πr²
A = π × (9)² = π × 81 =
81π in²
Options:
A) 4.5π → nope
B) 81π → yes!
C) 9π → that’s just r, not r²
D) 18π → that’s 2×r, not helpful here
✔ Correct answer is
B
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Problem 3:
This time, the line shown is
10 cm, but it goes all the way across the circle — that’s the
diameter, not the radius!
So, radius = diameter ÷ 2 = 10 ÷ 2 =
5 cm
Now use A = πr² = π × (5)² = π × 25 =
25π cm²
Options:
A) 25π → perfect
B) 100π → that’s if you used diameter squared — wrong
C) 10π → nope
D) 5π → that’s just r, not r²
✔ Correct answer is
A
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Final Answer:
1. C
2. B
3. A
Parent Tip: Review the logic above to help your child master the concept of area and circumference of a circle worksheet answers.
