Question

need the lowest common multiples for:
1. 20 and 35
2. 28 and 35
3. 40 and 70
4. 52 and 160

Thanks

Answer 1

1. start with 35 till you hit something that 20 goes into

Answer 2

same for the rest really

Answer 3

1. 140
2. 140
3. 280
4. 2080

Answer 4

20/35 = 1

4/7 = 1
*4 *4
--------
28/7 = 4

Answer 5

35*4 = 140

Answer 6

We need to find the smallest number that both integers divide evenly. So take the larger of the two and start multiplying it by 2, 3, 4 etc. until we find a number the smaller number divides evenly.

take 20 and 35:
2 * 35 = 70 not divisible by 20
3 * 35 = 103 not divisible by 20
4 * 35 = 140 divisible 20 140/20 = 7
LCM of 20 and 35 = 140

A trick that my help is to take each term and factor it. Then ignore common factors and multiply the remainig factors together.

example 28 and 35:
28 = 4 x 7
35 = 5 x 7

so try 4 x 5 x 7 = 140

So LCM of 28 and 35 = 140

Answer 7

3) 40 and 70

40/70 = 1

4/7 = 1

28/7 = 4

70*4 = 280