An easy question on work problems for P3–P4, with a step-by-step solution, diagrams and the answer. Common in the Hua Xia Cup's P3 to P6 papers; harder ones have someone leaving partway, people taking turns, or cows grazing a field that keeps growing.
The question
Before the Dragon Boat Festival, Grandma and Mum wrap rice dumplings together.
Grandma wraps 7 an hour and Mum 5 an hour.
They start at the same time and need 24 dumplings in all.
How many hours will it take them?
Show the hints (2)
💡Hint 1: Each hour, how many do the two of them wrap together?
💡Hint 2: How many 'one hour's worth' are there in 24?
Worked solution
Have a go first, then read the solution step by step.
1.Together they wrap 7 + 5 = 12 an hour.
2.How many lots of 12 make 24? 24 ÷ 12 = 2 hours.
⚠️Common mistake: dividing by one person's rate. Both are wrapping at the same time.
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