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| Answer:All prime numbers including 1. |
| Imagine numbers 1 to 100. |
| Boxer 1 will be by himself. No one knocks him and he won’t fight. |
| Boxer 2 knocks out all even ones 4, 6, 8, …,100. We are left with 1,2,3,5,7,9,11,13, …99. |
| Boxer 3 knocks out all multiples of 3 starting from 6 (already knocked out by 2) including 9, 15,21, … 99. |
| Boxer 4 is been knocked out by boxer 2. So he can’t fight. |
| Boxer 5 knocks out five multiples 25, 35, 55, 65, 85, 95 |
| (boxers 10, 15, 20, 30, 40, 45, 50 etc. are been knocked out already). |
| Boxer 6 is been knocked out by 2. So he can’t fight. |
| Boxer 7 knocks out seven multiples starting 14 (knocked already). |
| Boxers 21, 28, 35, 42, 56, 63, 70, 84, 98 are been knocked out. So boxer 7 knocks out 49, 77, 91. |
| So left out boxers are 1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97. |
| Total 26 boxers left. |
| Illustration conveys how to identify prime numbers. So prime numbers and 1 are in the list. |
| Winners:Rejeswararao Ainapurapu. |
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