Question

Which of the following is the LCM of 7, 14 and 21? a) 42 b) 46 c) 40 d) 7​

Answer 1

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✣ We can find L.C.M by three different methods.

• By listing multiples.

• By Prime factorization method.

• By Division method.

 

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✣ Let's solve this by Listing Multiples.

7 $\longmapsto$ 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105, 112, 119, 126, 133, 140, 147, 154, 161, 168, 175, 182.

14 $\longmapsto$ 14, 28, 42, 56, 70, 84, 98, 112, 126, 140, 154, 168, 182, 196, 210, 224, 238, 252, 266, 280.

21 $\longmapsto$ 21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, 252, 273, 294, 315, 336, 357, 378, 399, 420.

Common multiples $\twoheadrightarrow$ 42, 84, 126, 168.

L.C.M $\twoheadrightarrow$ 42.

Hence, Option A is correct answer.

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Learn More!

• L.C.M refers to lowest common factor or least common factor. You can say that lowest and least have same meanings.