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The edges of a triangular board are 6 cm, 8 cm and 10 cm. The cost of painting it 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

Solution:

Given, the edges of a triangular board are 6 cm, 8 cm and 10 cm.

We have to find the cost of painting it at the rate of 9 paise per cm²

Given, a = 6 cm

b = 8 cm

c = 10 cm

Area of triangle = √s(s - a)(s - b)(s - c)

Where s= semiperimeter

s = (a + b + c)/2

Now, s = (6 + 8 + 10)/2

= 24/2

s = 12 cm

Area of triangle = √[12(12 - 6)(12 - 8)(12 - 10)]

= √[12(6)(4)(2)]

= √[12(24)(2)]

= √[12 × 12 × 2 × 2]

= 12 × 2

Area = 24 cm²

The cost of painting area of 1 cm² = 9 paise

Cost of painting entire area = 24 × 9

= 216 paise

= 216/100

= Rs. 2.16/-

Therefore, the cost of painting the triangular board is Rs. 2.16/-

✦ Try This: The edges of a triangular board are 7 cm, 8 cm and 9 cm. The cost of painting it at the rate of Rs. 1.50 per cm² is

☛ Also Check: NCERT Solutions for Class 9 Maths Chapter 12

NCERT Exemplar Class 9 Maths Exercise 12.1 Problem 9

The edges of a triangular board are 6 cm, 8 cm and 10 cm. The cost of painting it 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

Summary:

The edges of a triangular board are 6 cm, 8 cm and 10 cm. The cost of painting it at the rate of 9 paise per cm² is Rs. 2.16/-

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