Final answer:
The common denominator for 1/2 and 1/4 is 4, as it is the smallest number that is a multiple of both 2 and 4, allowing the fractions to be compared or combined.
Step-by-step explanation:
Elise is doing her homework and wants to find a common denominator for 1/2 hour and 1/4 hour. A common denominator is a shared multiple of the denominators of two or more fractions. In this case, the denominators are 2 and 4. The smallest number that is a multiple of both 2 and 4 is 4. Therefore, the common denominator for 1/2 and 1/4 is 4. This means you can express 1/2 as 2/4 because 1 times 2 equals 2, and the original denominator (2) times 2 equals 4. Similarly, 1/4 can stay as it is because its denominator is already 4.
To recap, to find a common denominator, you can list the multiples of the denominators or use the largest denominator when it is a multiple of the smaller one. Therefore, 4 is the smallest number that can be a common denominator for fractions with denominators of 2 and 4.