Find the LCM of 84, 105 and 140.

Correct option is C

Given: 

To find ; LCM ​(Least Common Multiple) of 84,.105, and 140, 

Concept Used: 

 The LCM, take the highest powers of all the prime factors that appear in any of the numbers

Solution:  

Prime factorizations: 

​$$84 = 2 \times 3 \times 7 \\ \ \\ 105 = 3 \times 5 \times 7 \\ \ \\ 140 = 2 \times 2 \times 5 \times 7$$ 

Now,  LCM = $$2^2 \times 3 \times 7 \times 5$$​​

So, the LCM of 84, 105, and 140 is 420.