Friend of 12 and 21

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Computing the least common multiple

$Lcm (a,b = \frac{|a \times b|}{Gcd(a,b)}$

$Gcd (12,21) = 3$

$12 = 2^{2} \times 3$ and $21= 3 \times 7$ , Thus We Have $Gcd = 3$

$Lcm = \frac{12 \times 21}{3} = \frac{252}{3} = 84$

Answer Is $\boxed{84}$

12 = 3 X 4.

21 = 4 X7.

lcm(12,21) = 3 X 4 X 7 = 84.

Just use the algorithm method and u will get the answer

Simply first find out the common factor/s between 12 & 21 followed by multiplying the remaining uncommon factors

12 = 12 , 24 , 36 , .... , 84 . 21 = 21, 42 , 63 , 84 . ; The answer is 84

LCM OF 12 AND 21 WILL BE 84. 2X2X3X7= 84

Least Common Multiple is the smallest possible number that is a multiple of both.

The multiples of 12 up to 84 are: 12 24 36 48 60 72 84...

The multiples of 21 up to 84 are: 21 42 63 84

Therefore the least common multiple is 84.

lcm of 12 and 21 is 84.

12 = 2^{2} x 3 and 21 = 3 x 7. so LCM of 12 and 21 is 2^{2} x 3 x 7 = 84.

First, list a few multiples of each number. Then, see the number that appears in both lists, first. That number is the least common multiple. The correct answer is 84.

12=3 x 4 , 21= 3 x 7 , L C M= 3 X 7 X 4=84

You should use Multiplication for larger number . 21x2 = 42 . 42 /12 = 7/2 ( Wrong ) 21x3 = 63 . 63/12 = 21/4 ( Wrong ) 21x4 = 84 . 84/12 = 7 ( True ) That's why you choose 84 .

to find the least common multiple, first we need to prime factorise i.e. 12 = 3 * 2 * 2 21 = 3 * 7 So the 3 is common and to find the L.C.M (lowest common multiple), L.C.M. = Common factors * remaining factors = 3 * 4 * 7 = 84

The common multiples of 12:

12,24,36,48,60,84,...

The common multiples of 21:

21,42,63,84,...

From the two lists, we can see that 84 is the least common multiple.