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The diagram shows a triangular prism of length 7cm. The r...

The diagram shows a triangular prism of length 7cm. The right-angled triangle PQR is a cross-section of the prism |PR| = 5cm and |RQ| = 3cm. What is the area of the cross-section?

The diagram shows a triangular prism of length 7cm. The right-angled triangle PQR is a cross-section of the prism |PR| = 5cm and |RQ| = 3cm. What is the area of the cross-section?

A.

4cm2

B.

6cm2

C.

15cm2

D.

20cm2

Correct answer is B

In Δ RQP, QR2 + QP2 = RP2

32 + QP2 = 52

QP^2} = 5\(^2 - 32

QP = 16

= 4 cm 

Area = \frac{1}{2} \times base \times height

= \frac{1}{2} \times 3 \times 4

= 6 cm^2