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2 Given: The least number which when divided by 5, 6, 7 and 8 leaves a remainder 3 The least number when divided by 9 remainder = 0 Concept Used: For the least number take LCM and also check that all conditions are satisfying or not For same remainder in each case add the remainder in the LCM Calculation: First we have to find the LCM of 5, 6, 7, 8 5 = 51 6 = 21 × 31 7 = 71 8 = 23 LCM of 5, 6, 7, 8 is 23 × 31 × 51 × 71 = 840 For same remainder we have to add 3 to the LCM ⇒ 840 + 3 Now check weather it is divisible by 9 or not 843/9 = Not divisible by 9 Now we have to take next multiple of LCM and then add 3 840 × 2 + 3 ⇒ 1683 Divide it by 9 1683/9 = 187 ⇒ 1683 is divisible by 9 ⇒ 1683 is the least number when divided by 5, 6, 7, 8 gives remainder 3 Shortcut Trick The least number must be divisible by 9 For divisibility of 9 sum of digits of the number must be divisible by 9 Checking it by options: Option 1) 1677 1 + 6 + 7 + 7 = 21 ⇒ 1677 is not divisible by 9 Option 2) 1683 1 + 6 + 8 + 3 = 18 ⇒ 1683 is divisible by 9 Option 3) 2523 2 + 5 + 2 + 3 = 12 ⇒ 2523 is not divisible by 9 Option 4) 3363 3 + 3 + 6 + 3 = 15 ⇒ 3363 is not divisible by 9 ∴ The least number is 1683 which when divided by 5, 6, 7 and 8 leaves a remainder 3, but when divided by 9 leaves no remainder. |