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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 \(\Delta\) RQP, QR\(^2\) + QP\(^2\) = RP\(^2\)

3\(^2\) + QP\(^2\) = 5\(^2\)

QP\(^2} = 5\(^2\) - 3\(^2\)

QP = \(\sqrt{16}\)

= 4 cm 

\(\therefore\) Area = \(\frac{1}{2} \times base \times height\)

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

= 6 cm\(^2\)

Volume = 6 x 7

= 42 cm\(^3\)