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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 volume of the prism?

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 volume of the prism?

A.

28cm2

B.

42cm2

C.

70cm2

D.

84cm2

Correct answer is B

Volume of prism = Area x height

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

Volume = 6 x 7

= 42 cm^3