Question

The edges of a triangular board are 6 cm, 8 cm and 10 cm. The cost of painting to its surface on one side at the rate of 9 paise per cm² is

• A. Rs 2.00
• B. Rs 2.16
• C. Rs 2.48
• D. Rs 3.00

Answer 1

The correct option is B Rs 2.16

Explanation:
Given: a = 6cm, b= 8cm, c = 10 cm.
$S=\frac{(6+8+10)}{2}=12$
Hence, by using Heron’s formula, we can write:
$A=\sqrt{12(12-6)(12-8)(12-10)}=\sqrt{12\times 6\times 4\times 2}=\sqrt{576}=24c{m}^2$
Therefore, the lost of painting at a rate of 9 paise per $c{m}^2=24\times 9$ paise = Rs. 2.16.