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Find the number of zeroes at the end of the product 15!.1. 42. 33. 54. 2 |
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Answer» Correct Answer - Option 2 : 3 Given: 15! = 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8 × 9 × 10 × 11 × 12 × 13 × 14 × 15 Concept used: To find the number of zeroes at the end of the product, we need to calculate the number of 2’s and number 5’s or number of pairs of 2 and 5. 2 × 5 = 10 ⇒ Number of zeroes = 1 (number of pair = 1) The number of pairs of 2 and 5 is same as the number of zeroes at the end of the product Calculation: Given expression = 15! = 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8 × 9 × 10 × 11 × 12 × 13 × 14 × 15 In any factorial value, the number of 5’s is always lesser than the number of 2’s In the above expression, number of 5’s = 3 (5, 10 = 2 × 5, 15 = 3 × 5) Number of 2’s = 11 But total number of pairs of 2’s and 5’s = 3 ∴ The total number of zeroes is 3. |
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