Problem 18 · 2024 Math Kangaroo
Stretch
Arithmetic & Operations
groupingtotal-then-divide
Lucy weighs building blocks two at a time and reads these scale values: 200 g, 100 g and 240 g (see picture). How much do the three different building blocks weigh all together?
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Answer: A — 270 g
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Hint 1 of 2
Each reading is the weight of two of the three blocks together.
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Hint 2 of 2
Add the three known readings — that counts every block twice.
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Approach: add the pair-weights and halve
- The three readings 200, 100, 240 each weigh two blocks, so together they count all three blocks twice.
- Sum: 200 + 100 + 240 = 540 grams.
- Half of that is the weight of the three blocks once: 540 ÷ 2 = 270.
- Answer: 270 g (A).
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