Explain why, when we add $\frac{1}{4}+\frac{3}{8}$, we can change both fractions to a common denominator in order to find the sum.



Choose the correct answer below.

AWe can change both fractions to a common denominator so that they have equal-sized parts. We can't add different-sized parts. In this case, we can make the parts the same size. We have $\frac{1}{4}=\frac{2}{8}$ and so $\frac{1}{4}+\frac{3}{8}=\frac{2}{8}+\frac{3}{8}=\frac{2+3}{8}=\frac{5}{8}$.
BWe can change both fractions to a common numerator so that they have equal-sized parts. We can't add different-sized parts. In this case, we can make the parts the same size. We have $\frac{1}{4}=\frac{3}{12}$ and so $\frac{1}{4}+\frac{3}{8}=\frac{3}{12}+\frac{3}{8}=\frac{3}{12+8}=\frac{3}{20}$.
CWe can change both fractions to a common denominator so that they have equal-sized parts. We can't add different-sized parts. In this case, we can make the parts the same size. We have $\frac{1}{4}=\frac{1}{8}$ and so $\frac{1}{4}+\frac{3}{8}=\frac{1}{8}+\frac{3}{8}=\frac{1+3}{8}=\frac{4}{8}=\frac{1}{2}$.
DWe can change both fractions to a common denominator so that they have equal-sized parts. We can't add different-sized parts. In this case, we can make the parts the same size. We have $\frac{1}{4}=\frac{2}{8}$ and so $\frac{1}{4}+\frac{3}{8}=\frac{2}{8}+\frac{3}{8}=\frac{2+3}{8+8}=\frac{5}{16}$.

Verified Answer :

  • To add fractions, convert them to a common denominator to ensure parts are of equal size.
  • \(\frac{1}{4}\) converts to \(\frac{2}{8}\).
  • Add the numerators of the common-denominator fractions: \(\frac{2}{8} + \frac{3}{8} = \frac{2+3}{8} = \frac{5}{8}\).
  • Option A is the only choice that reflects this correct logic and calculation.
  • Final Answer: \(\boxed{A}\)

Explanation

  1. Understanding the Need for a Common Denominator

To add fractions like \(\frac{1}{4}\) and \(\frac{3}{8}\), it is essential that the parts we are adding are of the same size. A fraction represents parts of a whole, and the denominator tells us how many equal-sized parts the whole is divided into. Here, \(\frac{1}{4}\) means 1 part out of 4, while \(\frac{3}{8}\) means 3 parts out of 8. Because these "parts" (fourths and eighths) have different sizes, we cannot add them directly. We must first convert them into a common unit of measurement, which is done by finding a common denominator.

  1. Converting and Adding the Fractions

The denominators are 4 and 8. The least common multiple of 4 and 8 is 8. Therefore, we want both fractions to have 8 as the denominator. We already have \(\frac{3}{8}\). For \(\frac{1}{4}\), we can multiply both the numerator and the denominator by 2 to keep the value the same:
\[\frac{1}{4} = \frac{1 \times 2}{4 \times 2} = \frac{2}{8}\]
Now both fractions have the same denominator, allowing us to combine the parts:
\[\frac{1}{4} + \frac{3}{8} = \frac{2}{8} + \frac{3}{8}\]
When the denominators are the same, we simply add the numerators and keep the denominator constant:
\[\frac{2 + 3}{8} = \frac{5}{8}\]

  1. Conclusion

Comparing our result and reasoning with the provided options:

  • Option A correctly states that we need equal-sized parts, performs the conversion \(\frac{1}{4} = \frac{2}{8}\), and correctly adds the numerators while keeping the denominator the same to get \(\frac{5}{8}\).
  • Option B suggests using a common numerator and performs an incorrect addition.
  • Option C uses an incorrect conversion (\(\frac{1}{4} = \frac{1}{8}\)).
  • Option D correctly converts the fraction but uses an incorrect addition rule (\(8+8=16\)).

Therefore, Option A is the correct answer. The smallest possible value is \(\boxed{A}\).

Examples

Adding fractions with different denominators is like trying to add different currencies without converting them to a common base. For example, if you have 1/4 of a dollar (25 cents) and 3/8 of a dollar (37.5 cents), you can't just add "1" and "3" to get 4. Instead, you convert them both to the same unit (cents) to get 25 + 37.5 = 62.5 cents, or 5/8 of a dollar. This process of finding a "common denominator" ensures that you are adding comparable values, just like converting different units into a standard, universal unit in measurement or finance.