A good strategy for looking for common denominators is to check 2, 3 and/or 5 first.
Since multiples of 5 always end in either 0 or 5, you can eliminate that.
Since multiples of 2 are always even numbers, you can eliminate that from 81.
When you try 3:
81 / 3 = 27
24 / 3 = 8
There 3 is A common denominator. Other numbers may have multiple common denominators (like 30 and 90 which have 2, 3, 5, 6, 15 and 30 in common). So be sure you observe what your question is specifically asking.
common denominator of eight and nine
8100
Since 8 is 23 and 81 is 34, the least common denominator is 23 x 34 = 648.
4536
the number 9
To compare the fractions 28/81 and 7/24, we need to find a common denominator. In this case, the least common multiple of 81 and 24 is 81. We then convert both fractions to have a denominator of 81: 28/81 = 28/81 and 7/24 = 21/81. Now that both fractions have the same denominator, we can compare the numerators directly. Since 28 is greater than 21, the fraction 28/81 is greater than 7/24.
common denominator of eight and nine
The LCD of the fractions 8/81 and 7/24 is 648.
3
Their product.
8100
Since 8 is 23 and 81 is 34, the least common denominator is 23 x 34 = 648.
A common denominator is 72.
4536
the number 9
A common denominator 24.
A common denominator, though not the least one, is 24*21 = 504.