Question

A circular signboard has a radius of 2 m. If painting costs ₹60 per m² and 10% of the board is left unpainted, what is the total painting cost?

• A. ₹658.2
• B. ₹678.6
• C. ₹630.4
• D. ₹681.9

Answer 1

Answer:

B. ₹678.6

Radius of the signboard:

$r = 2 \text{ m}$

Area of the circle:

$A=\pi r^2=\frac{22}{7}\times 2^2=\frac{88}{7}\text{ m}^2$

Since 10% is left unpainted, 90% is painted:

$\text{Painted area}=\frac{90}{100}\times \frac{88}{7}$
$=\frac{396}{35}\text{ m}^2$

Painting cost at ₹60 per m²:

$\text{Cost}=\frac{396}{35}\times 60$
$=\frac{23760}{35}$
$\approx 678.6$