Consider the expression 63 + 81.

How can you use the distributive property and the GCF to find an equivalent expression? Explain how you can check your answer.

1 answer

To use the distributive property and the greatest common factor (GCF) to find an equivalent expression for \( 63 + 81 \), we start by identifying the GCF of the two numbers.

  1. Finding the GCF:

    • The prime factorization of \( 63 \) is \( 3^2 \times 7 \) (since \( 63 = 3 \times 21 = 3 \times 3 \times 7 \)).
    • The prime factorization of \( 81 \) is \( 3^4 \) (since \( 81 = 3 \times 27 = 3 \times 3 \times 9 = 3 \times 3 \times 3 \times 3 \)).
    • The common prime factor is \( 3 \). The lowest power of \( 3 \) that appears in both factorizations is \( 3^2 \).
    • Thus, the GCF of \( 63 \) and \( 81 \) is \( 9 \).
  2. Applying the Distributive Property:

    • We can express \( 63 \) and \( 81 \) in terms of their GCF:
      • \( 63 = 9 \times 7 \)
      • \( 81 = 9 \times 9 \)
    • Using these forms, we can rewrite the original expression: \[ 63 + 81 = 9 \times 7 + 9 \times 9 \]
    • Now, we apply the distributive property: \[ 63 + 81 = 9(7 + 9) \]
  3. Simplifying the Expression:

    • Calculate \( 7 + 9 \): \[ 7 + 9 = 16 \]
    • Therefore, we have: \[ 63 + 81 = 9 \times 16 \]
  4. Checking Your Answer:

    • Now we can check our answer by evaluating both forms of our expression:
      • First, directly calculate \( 63 + 81 \): \[ 63 + 81 = 144 \]
      • Next, calculate \( 9 \times 16 \): \[ 9 \times 16 = 144 \]
    • Since both calculations yield the same result, \( 144 \), we have confirmed that \( 63 + 81 \) is indeed equivalent to \( 9(7 + 9) \) or \( 9 \times 16 \).

In conclusion, using the distributive property and the GCF, we found that: \[ 63 + 81 = 9(7 + 9) \quad \text{or} \quad 63 + 81 = 9 \times 16 \] And we checked our answer by confirming both calculations produce the same result, \( 144 \).