At each corner of a triangular field of sides 26 m, 28 m

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At each corner of a triangular field of sides 26 m, 28 m and 30 m, a cow is tethered by a rope of length 7 m. The area (in m²) ungrazed by the cows is

1. 336
2. 259
3. 154
4. 77

Correct Option: B

Using Rule 17,

Area grazed by all cows =	180°	πr² =	πr²
	360°		2

=	1	×	22	× 7 × 7 = 77 sq.metre
	2		7

Semi-perimeter of triangular field

S =	26 + 28 + 30	= 42 metres
	2

∴ Area of the field = √s(s - a)(s - b)(s - c)
= √42(42 - 26)(42 - 28)(42 - 30)
= √42 × 16 × 14 × 12 = 336 sq.metre
∴ Area ungrazed by the cows = 336 – 77 = 259 sq.metre