Problem 11 · 2017 Math Kangaroo
Stretch
Arithmetic & Operations
substitution
Every box shows the result of the addition of the numbers on the very left and on the very top (for example: \(5 + 7 = 12\)). Which number is written behind the star?
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Answer: B — 11
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Hint 1 of 2
Each cell equals its row number plus its column number; use the filled cells to find the hidden row number.
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Hint 2 of 2
Once you know the missing row label, add it to the star's column heading.
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Approach: recover the hidden labels, then add
- Each box is row-label + column-label. The cell '14' sits in the star's row under column 10, so the hidden row label is 14 - 10 = 4.
- The star is in that same row (label 4) under column 7.
- So the star = 4 + 7 = 11.
- The number behind the star is 11.
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