2025 AMC 10A Problems/Problem 21
(Problem goes here)
Solution 1
Let our subset be 
If we add any one element from the set 
we will have to remove at least one element from our current subset. Hence, the size of our set cannot exceed 
~Tacos_are_yummy_1
Solution 2
Let our subset be 
Since odd numbers + odd numbers will always sum to an even number, this subset holds true. The addition of any even number will result in a violation of the rule, so the maximum number of elements is
~KMS888
See also
| 2025 AMC 10A (Problems • Answer Key • Resources) | ||
| Preceded by Problem 20 |
Followed by Problem 22 | |
| 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
| All AMC 10 Problems and Solutions | ||
| 2025 AMC 12A (Problems • Answer Key • Resources) | |
| Preceded by Problem 17 |
Followed by Problem 19 |
| 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | |
| All AMC 12 Problems and Solutions | |
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