What is the least number which, when doubled, is exactly divisible by 12, 18, 21, and 30?
Aptitude
Problems on H.C.F and L.C.M
Difficulty: Easy
Choose an option
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A315
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B420
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C540
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D630
Answer
Correct Answer: 630
Explanation
Concept / Approach
- Let the required number be n. Then 2n must be a common multiple of 12, 18, 21, and 30.
- The least such multiple is the LCM; hence take n = LCM/2.
Step-by-step calculationLCM(12,18,21,30) = 12602n = 1260 ⇒ n = 1260/2 = 630
Verification2×630 = 1260 which is divisible by 12, 18, 21, and 30.
Final Answer630