The diagram shows a triangular prism with /QR/ = /MN/ = /OP/ = 10 cm and /NR/ = /QM/ = 8 cm. If ∠RON = 90o and ∠RNO = 30o, calculate, correct to 3 significant figures, the volume of the prism.

(b) A bird on top of a tree sights a prey 18 m away and on the same horizontal ground as the foot of the tree. If the height of the tree is 8 m, calculate, correct to the nearest degree, the angle of depression through which the bird sights the prey.

The Chief Examiner reported that this question was not as popular as question 1. Candidates’ performance in this question was also reported to be poor. Majority of the candidates could not calculate the volume of the prism as required. In part (a) candidates were expected to respond as follows:
|RO| = 8 Sin 30o = 4 cm. |NO| = 8Cos30o = cm. Area of triangle
RNO = ½ x 4 x = cm2. Volume of prism = area of cross section x height = x 10 = = 80 x 1.732 = 138.56 = 139.0 cm2, correct to 3 significant figures.

In part(b) candidates were expected to represent the information in a diagram.
B

8m

18m
G P
From the diagram, tan x = , where x = required angle of depression. This implied that x = tan-1 = 24o, correct to the nearest degree.