Problem 10 · 2013 Math Kangaroo
Medium
Arithmetic & Operations
estimate-and-pick
Which of the following numbers is biggest?
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Answer: C — \(20\times\sqrt{13}\)
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Hint 1 of 2
Square each expression to remove the awkward roots, then compare the results.
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Hint 2 of 2
After squaring, you are just comparing plain numbers.
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Approach: square each option and compare
- Square each value: A→260, B→3380, C→5200, D→1809, E→2013.
- The largest square is 5200, from option C (20 · √13).
- So the biggest number is 20 × √13.
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