NAPLAN NAPLAN Numeracy Year 9 Practice 2 — Questions and Answers
Question 1: A bag contains 5 red marbles, 3 blue marbles and 2 green marbles. If one marble is chosen at random, what is the probability of choosing a red marble?
- 1/5
- 1/2 (Correct answer)
- 3/10
- 2/5
Correct answer: 1/2
Total marbles = 10. P(red) = 5/10 = 1/2
Total marbles = 5 + 3 + 2 = 10. P(red) = 5/10 = 1/2. There is a 50% chance of picking a red marble.
Question 2: A sequence of figures is made with matchsticks: Figure 1 uses 4, Figure 2 uses 7, Figure 3 uses 10. How many matchsticks are needed for Figure 8?
- 22
- 25 (Correct answer)
- 28
- 31
Correct answer: 25
Rule: 3n + 1. Figure 8 = 3(8) + 1 = 25
The sequence 4, 7, 10, ... increases by 3 each time. General rule: matchsticks = 3n + 1. For Figure 8: 3(8) + 1 = 25.
Question 3: A car travels 360 km using 45 litres of petrol. What is the car's fuel efficiency in kilometres per litre?
- 6 km/L
- 7 km/L
- 8 km/L (Correct answer)
- 9 km/L
Correct answer: 8 km/L
Fuel efficiency = 360 ÷ 45 = 8 km/L
Fuel efficiency = 360 km ÷ 45 L = 8 km per litre. The car travels 8 kilometres for every litre of petrol consumed.
Question 4: A stem-and-leaf plot shows quiz scores: Stem 5: leaves 2 4 7 Stem 6: leaves 1 3 3 8 Stem 7: leaves 0 5 9 Stem 8: leaves 2 6 What is the median score?
- 63
- 65 (Correct answer)
- 68
- 70
Correct answer: 65
12 values in order: 52,54,57,61,63,63,68,70,75,79,82,86. Median = (63+68)/2 = 65.5 ≈ 65
The ordered data: 52, 54, 57, 61, 63, 63, 68, 70, 75, 79, 82, 86 (12 values). Median = average of 6th and 7th values = (63 + 68) ÷ 2 = 65.5, closest to 65.
Question 5: A rectangular block of wood measures 8 cm × 5 cm × 3 cm. What is its total surface area?
- 79 cm²
- 120 cm²
- 158 cm² (Correct answer)
- 240 cm²
Correct answer: 158 cm²
SA = 2(8×5 + 8×3 + 5×3) = 2(40+24+15) = 2×79 = 158 cm²
SA = 2(length×breadth + length×height + breadth×height) = 2(8×5 + 8×3 + 5×3) = 2(40 + 24 + 15) = 2 × 79 = 158 cm².
Question 6: In a class of 30 students, the ratio of boys to girls is 2 : 3. How many girls are in the class?
- 10
- 12
- 15
- 18 (Correct answer)
Correct answer: 18
Total parts = 5. Girls = (3/5) × 30 = 18
Ratio 2:3 gives 5 total parts. Girls = (3/5) × 30 = 18. Check: boys = (2/5) × 30 = 12, and 12 + 18 = 30 ✓
Question 7: A straight angle is divided into three parts. Two of the angles are 47° and 65°. What is the third angle?
- 58°
- 68° (Correct answer)
- 78°
- 88°
Correct answer: 68°
Straight angle = 180°. Third angle = 180 − 47 − 65 = 68°
Angles on a straight line sum to 180°. Third angle = 180° − 47° − 65° = 180° − 112° = 68°.
NAPLAN NAPLAN Numeracy Year 9 Practice 2
A bag contains 5 red marbles, 3 blue marbles and 2 green marbles.
If one marble is chosen at random, what is the probability of choosing a red marble?