A roll of stickers repeats the pattern triangle ▲, circle ●, diamond ◆, circle ●, then triangle ▲ again, and so on. Ali cut out a length of the roll that contains exactly 13 triangles ▲. What is the greatest possible number of circles ● in the length he cut out?
Need a hint?
Think about the gaps between triangles: how many gaps lie between the triangle before your piece and the triangle after it?
Worked answer
- Each repeat of 4 stickers has 1 triangle ▲ and 2 circles ●.
- The longest piece with exactly 13 triangles starts just after the triangle before its first one and ends just before the triangle after its last one.
- That piece covers 14 gaps between consecutive triangles, and each gap holds 2 circles.
- 14 × 2 = 28, so the greatest number of circles is 28.
Answer: 28 circles
The mistake this question tests
Habit
Factors and multiples (HCF, LCM)
Counting only the 12 gaps between the first and last triangle gives 12 × 2 = 24, which leaves out the circles at both ends of the piece.
How to fix it at home →More PSLE whole numbers questions
Short answer · 2m
Write down all the common factors of 18 and 30
See the answer →Structured · 4mA school has lockers numbered 1 to 200
See the answer →MCQ · 1mRound 456 789 to the nearest ten thousand
See the answer →Short answer · 2mThere are some stickers in a box
See the answer →Structured · 3mThe seats on a school excursion bus were arranged in rows
See the answer →MCQ · 2mNadia sorted 108 red buttons and 144 blue buttons into storage boxes for a craft project
See the answer →Practise PSLE whole numbers until the mistakes stop.
Three PSLE questions, free, no sign-up. You’ll see exactly where the marks went. Then 7 days of everything for S$4.99.