What is the lowest common multiple of 5, 7 and 10?

2 Answers
Feb 13, 2018

The answer is 70.

Explanation:

To find the LCM (Lowest common multiple) of a set of numbers, you first find the multiples of each number and then identify the smallest common one among the set.

In this case, using 5, 7, and 10. The smallest common multiple of each would be 70. If we find the multiples of each of the numbers, we can see that no other number before 70 is common to all of them.

Multiples of 5: " "5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, ...

Multiples of 7: " "7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, ...

Multiples of 10: " "10, 20, 30, 40, 50, 60, 70, 80, ...

If you realize, the only common multiple up to this point is 70. There may be other common multiples but you are looking for the smallest (or lowest) one.

Note: The way you find multiples is to multiply the number you are trying to find numbers for by each number in succession.

For example, multiples of 3: 3(3*1), 6(3*2), 9(3*3), 12(3*4), 15(3*5), ...

Hope this helps!!

Feb 17, 2018

70

Explanation:

You do not need to consider 5 at all the calculation, because it is a factor of 10. So any number divisible by 10 will automatically be divisible by 5 as well.

7 and 10 do not have any common factors (other than 1), so their LCM will be their product.

:. LCM = 7 xx10 = 70

You can use prime factors to find this as well;

" "5 = color(white)(www) 5
" "7 =color(white)(wwwww) 7
" "10 = ul(2 xx 5color(white)(www))

LCM = 2 xx 5 xx 7 = 70