Unit 3
4 marks · EasyA triangle has sides of lengths 9 cm, 12 cm and 15 cm.
State whether this triangle is a right triangle. Show your reasoning using Pythagoras’ Theorem.
List all the multiples of 9 up to 36.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Yes; 9^2 + 12^2 = 15^2, so it is a right triangle.
(b) 9, 18, 27, 36
Also accept: 9, 18, 27, 36
Common mistakes: Incorrect calculation of squares; Missing first multiple (9 itself) or skipping a multiple
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly calculates 9^2 + 12^2 and compares to 15^2.
A1 (a) · 1 mark · States 'yes', giving a correct reason (equality shown). (follow-through)
B1 (b) · 2 marks · Lists all multiples of 9 up to 36: 9, 18, 27, 36 (all required for 2 marks, 1 mark for some correct).
Worked solution
a) Check if 9² + 12² = 15²: 9 × 9 = 81, 12 × 12 = 144, 15 × 15 = 225. 81 + 144 = 225, so it is a right triangle.
b) Multiples of 9 up to 36 are: 9, 18, 27, 36.