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?
Attached Figure / Diagram
A
4 cm2
B
6cm2
C
15cm2
D
20cm2
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
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\(^2\)
Source: Myschool Past Questions Archive (Record #26517)