The GCF of 10 and 28 is 2. The LCM of 10 and 28 is 140.
Factors of 10: 1, 2, 5, 10.
Factors of 28: 1, 2, 4, 7, 14, 28.
Common factors: 1 and 2. The greatest of these is 2.
10 = 2 × 5
28 = 2 × 2 × 7
GCF: multiply the prime factors both numbers share: 2 = 2.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 2 × 5 × 7 = 140.
Divide the larger number by the smaller and repeat with the remainder until it is 0. The last non-zero remainder is the GCF.
The last non-zero remainder is 2, so GCF(10, 28) = 2.
Multiples of 10: 10, 20, 30, 40, 50, 60, 70, 80, 90, ...
Multiples of 28: 28, 56, 84, 112, 140, 168, ...
The first number in both lists is 140.
2 × 140 = 280 = 10 × 28. This always holds for two numbers, so you can find the LCM as (10 × 28) ÷ 2 = 140.
Divide the top and bottom by the GCF 2: 10/28 = 5/14.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 10 | 2 | 10 |
| 3 and 10 | 1 | 30 |
| 4 and 10 | 2 | 20 |
| 5 and 10 | 5 | 10 |
| 6 and 10 | 2 | 30 |
| 7 and 10 | 1 | 70 |
| 2 and 28 | 2 | 28 |
| 3 and 28 | 1 | 84 |
| 4 and 28 | 4 | 28 |
| 5 and 28 | 1 | 140 |
| 6 and 28 | 2 | 84 |
| 7 and 28 | 7 | 28 |
See also: factors of 10 · factors of 28.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.