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How many numbers between 1 and 400 are exactly divisible by 7. |
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Answer» The concept of arithmetic progressions shall be applied here. ⚫So , the first number divisible by SEVEN is 1. Therefore our first term (a) becomes 7. ⚫Continuing the series we have , This forms an AP with →first term a = 7 →Common Difference d = 7 (a2 - a1) → Last term L = 399 → Number of TERMS (n) = ? ✔Using the formula , => L = a + (n-1) d ↪399 = 7 + (n-1)7 ↪392/7 = n - 1 ↪56 = n - 1 |
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