Find the area of an isosceles triangle whose base is 54 cm long and each equal side is 45 cm long.

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RRB NTPC CBT 2 Level -4 Official paper (Held On: 10 May 2022 Shift 1)
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  1. 1944 sq.cm
  2. 1215 sq.cm
  3. 972 sq.cm
  4. 1620 sq.cm

Answer (Detailed Solution Below)

Option 3 : 972 sq.cm
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Detailed Solution

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Given:

The area of an isosceles triangle whose base is 54 cm long and each equal side is 45 cm long.

Formula used:

Area of an isosceles triangle = 1/2 × b × √a2 – (b/2)2

Calculation:

Let the equal sides of an isosceles triangle be a cm and base be of b cm respectively

According to the question

Area of an isosceles triangle = 1/2 × b × √[a2 – (b/2)2]

⇒ 1/2 × 54 × √[452 – (54/2)2]

⇒ 27 × √2025 – (27)2

⇒ 27 × √(2025 – 729)

⇒ 27 × √1296

⇒ (27 × 36) cm2

⇒ 972 cm2

∴ The required area is 972 sq.cm

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