The GCF of 15 and 24 is 3. The LCM of 15 and 24 is 120.
Factors of 15: 1, 3, 5, 15.
Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24.
Common factors: 1 and 3. The greatest of these is 3.
15 = 3 × 5
24 = 2 × 2 × 2 × 3
GCF: multiply the prime factors both numbers share: 3 = 3.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 2 × 2 × 3 × 5 = 120.
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 3, so GCF(15, 24) = 3.
Multiples of 15: 15, 30, 45, 60, 75, 90, 105, 120, 135, ...
Multiples of 24: 24, 48, 72, 96, 120, 144, ...
The first number in both lists is 120.
3 × 120 = 360 = 15 × 24. This always holds for two numbers, so you can find the LCM as (15 × 24) ÷ 3 = 120.
Divide the top and bottom by the GCF 3: 15/24 = 5/8.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 15 | 1 | 30 |
| 3 and 15 | 3 | 15 |
| 4 and 15 | 1 | 60 |
| 5 and 15 | 5 | 15 |
| 6 and 15 | 3 | 30 |
| 7 and 15 | 1 | 105 |
| 2 and 24 | 2 | 24 |
| 3 and 24 | 3 | 24 |
| 4 and 24 | 4 | 24 |
| 5 and 24 | 1 | 120 |
| 6 and 24 | 6 | 24 |
| 7 and 24 | 1 | 168 |
See also: factors of 15 · factors of 24.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.