The GCF of 8 and 9 is 1. The LCM of 8 and 9 is 72.
8 and 9 share no common factor except 1, so they are coprime (relatively prime). When two numbers are coprime their LCM is simply their product: 8 × 9 = 72.
Factors of 8: 1, 2, 4, 8.
Factors of 9: 1, 3, 9.
Common factors: 1. The greatest of these is 1.
8 = 2 × 2 × 2
9 = 3 × 3
GCF: multiply the prime factors both numbers share: there are none, so the GCF is 1.
LCM: multiply every prime the maximum number of times it appears in either number: 2 × 2 × 2 × 3 × 3 = 72.
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 1, so GCF(8, 9) = 1.
Multiples of 8: 8, 16, 24, 32, 40, 48, 56, 64, 72, ...
Multiples of 9: 9, 18, 27, 36, 45, 54, 63, 72, 81, ...
The first number in both lists is 72.
1 × 72 = 72 = 8 × 9. This always holds for two numbers, so you can find the LCM as (8 × 9) ÷ 1 = 72.
8/9 is already in lowest terms because the GCF of 8 and 9 is 1.
| Numbers | GCF | LCM |
|---|---|---|
| 2 and 8 | 2 | 8 |
| 3 and 8 | 1 | 24 |
| 4 and 8 | 4 | 8 |
| 5 and 8 | 1 | 40 |
| 6 and 8 | 2 | 24 |
| 7 and 8 | 1 | 56 |
| 2 and 9 | 1 | 18 |
| 3 and 9 | 3 | 9 |
| 4 and 9 | 1 | 36 |
| 5 and 9 | 1 | 45 |
| 6 and 9 | 3 | 18 |
| 7 and 9 | 1 | 63 |
See also: factors of 8 · factors of 9 · 8/9 as a decimal.
Different numbers? Use the GCF and LCM calculator (any amount of numbers) or browse all GCF and LCM pairs.