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Find the sum of 3 digit numbers not divisible by 7. |
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Answer» Answer: Sum of all three digit NUMBERS which are not DIVISIBLE by 7 = Sum of all three digit numbers – Sum of all three digit numbers which are divisible by 7 Sum of all three digit numbers = 100 + 101 + 102 +...... + 999 [ The series is in A.P.] Sum of all three digit numbers which are divisible by 7 = 105 + 112 + ..... + 994 Let 994 be the nth term of the given series. ∴ 994 = 105 + (n – 1) × 7 ⇒ 7(n – 1) = 889 ⇒ n – 1 = 127 ⇒ n = 128 So, sum of all three digit numbers which are divisible by 7 ∴ Sum of all three digit numbers which are not divisible by 7 = 494500 – 70336 = 424164 |
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