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?
4cm2
6cm2
15cm2
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
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