Stage 9 · Unit 3 Open Questions
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Secondary 2 · Mathematics · Unit 3 Practice Test

Unit 3 Practice Test
20 Open Questions

Powers of 10 · Decimals · Compound Percentages · Bounds
20 questions · no multiple choice · 25 marks

✏️ One more round on Unit 3

Every answer is typed in — there are no options to guess from. Part A is ten quick one-line questions, one skill each. Part B is five short stories, where you have to work out which skill a question needs before you can use it. Two of the stories end with an animation that unlocks once you have answered their questions.

Unit Test 3 → Follow-up: Bounds & Powers → Retest: Bounds & Sig Figs →
Part A · Quick Lines Part B · Stories Going Viral The Goods Lift
⚡
Part A

Quick Lines

Toolkit:
  • Powers of 10 — a negative power makes a multiplication smaller and a division bigger.
  • Decimals — change the calculation into an equivalent one with whole numbers.
  • Percentages — turn each change into a multiplier.
  • Bounds — find the unit of rounding, halve it, and ask what kind of number was rounded.
Q1
Work out 0.072 × 10⁴
1 mark
Q2
Work out 5.6 ÷ 10⁻²
1 mark
Q3
Find the missing power: 830 × 10□ = 0.83
1 mark
Q4
Work out 0.6 × 0.07
1 mark
Q5
Work out 2.4 ÷ 0.08
1 mark
Q6
Write the multiplier for a 6% decrease.
1 mark
Q7
Round 0.004 739 to 2 significant figures.
1 mark
Q8
A pencil is 7.6 cm long, correct to 1 decimal place. What is the lower bound of its length?
1 mark
cm
Q9
A whole number is rounded to the nearest 100. The answer is 900. What is the upper bound?
1 mark
Q10
A tower is 340 m tall, correct to 2 significant figures. What is the upper bound of its height?
1 mark
m
QUICK LINES — PART SCORE
0/10
📖
Part B

Story Questions

Before you calculate: read the whole story, pick out the numbers you need, and decide which Unit 3 skill the question is really asking for. Some stories hide a trap for anyone who uses the numbers straight from the text.

🔬 Under the Microscope

In the science lab, Leo’s microscope makes everything look 10³ times wider than it really is.

Q11
A plant cell is really 0.025 mm wide. How wide does it look under Leo’s microscope?
1 mark
mm
Q12
Through the same microscope, a bacterium looks 2 mm wide. How wide is it really?
1 mark
mm

🍞 The Sourdough Bakery

Amira runs a small bakery. Each sourdough loaf uses 0.35 kg of flour, and her flour costs $1.20 per kg.

Q13
Amira opens an 8.4 kg sack of flour. How many loaves can she make from it?
2 marks
loaves
Q14
How much does the flour in one loaf cost, in dollars?
1 mark
$

📱 The Double Discount

A phone costs $480. On Friday the shop takes 25% off. On Monday it takes a further 10% off the Friday price.

Q15
What is the price of the phone on Monday?
2 marks
$
Q16
Jake says: “25% off and then 10% off is 35% off altogether.” What percentage of the original $480 has really been taken off?
2 marks
%

📈 Going Viral

Nina posts a video of her cat walking across a piano. It has 2000 views. Her friend predicts that the number of views will go up by 40% every day.

Q17
Using the prediction, how many views will the video have after 3 days?
1 mark
views
Q18
After how many days does the prediction first go above 10 000 views? You can use a calculator.
2 marks
days
Watch it happen: the prediction, one day at a time

🛗 The Goods Lift

A warehouse lift has a sign: Maximum load 450 kg, correct to the nearest 10 kg. Sam has to move crates of bottles. Each crate weighs 30 kg, correct to the nearest kg.

Sam must be certain the lift is never overloaded.

Q19
What is the lowest the real maximum load of the lift could be?
1 mark
kg
Q20
Sam works out 450 ÷ 30 = 15 and plans to load 15 crates. What is the largest number of crates Sam can load and still be certain the lift is safe?
2 marks
crates
Watch it happen: load the crates, worst case every time
STORY QUESTIONS — PART SCORE
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