The diagram shows a triangular prism of length 7cm. The right – angled triangle PQR…

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?

Correct Answer: Option B

Explanation

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)