A medium question on working backwards for P3–P4, with a step-by-step solution, diagrams and the answer. Working-backwards questions appear in the Hua Xia Cup's P1 to P5 first rounds, qualifying rounds and finals.
The question
May had some stickers.
She gave half to her sister, then 2 to a classmate, and had 6 left.
How many stickers did May have at first?
Show the hints (2)
💡Hint 1: Work backwards: how many did she have before giving 2 to her classmate?
💡Hint 2: That number was half of what she started with.
Worked solution
Have a go first, then read the solution step by step.
1.Before the classmate: the 6 left + the 2 given = 8.
2.That 8 was half, so she started with 8 × 2 = 16.
⚠️Common mistake: doubling first and answering 14. Undo the last step first.
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