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1. What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?
18 = 2 × 3 × 3
21 = 3 × 7
30 = 2 × 3 × 5
L.C.M. of 12, 18, 21 30= 2 × 3 × 2 × 3 × 7 × 5 = 1260
Required number = = 630
Solution:
12 = 2 × 2 × 318 = 2 × 3 × 3
21 = 3 × 7
30 = 2 × 3 × 5
L.C.M. of 12, 18, 21 30= 2 × 3 × 2 × 3 × 7 × 5 = 1260
Required number = = 630