Question

If the area of a circle is 154 cm², then find the circumference of the circle with radius (r + 3.5) cm.
1. 66 cm
2. 77 cm
3. 72 cm
4. 88 cm
5. 55 cm

Answer 1

Correct Answer - Option 1 : 66 cm

Given:

Area = 154 sq. cm

New radius = r + 3.5 

Concept used:

Area = πr2

Circumference of circle = 2 × π × r

Calculation:

πr2 = 154

r² = 154 × 7/22 = 49

Or, r = 7 cm

New radius = 7 + 3.5 = 10.5 cm

Circumference = 2 × (22/7) × 10.5 = 66 cm

∴ The circumference of the new circle is 66 cm.