To rewrite the sum \( 25 + 45 \) using their greatest common factor (GCF) and multiplication, we first need to find the GCF of 25 and 45.
The factors of 25 are: \( 1, 5, 25 \)
The factors of 45 are: \( 1, 3, 5, 9, 15, 45 \)
The GCF of 25 and 45 is \( 5 \).
Now, we can express \( 25 + 45 \) in terms of the GCF:
\[ 25 = 5 \times 5 \] \[ 45 = 5 \times 9 \]
This gives us:
\[ 25 + 45 = 5 \times 5 + 5 \times 9 = 5(5 + 9) \]
Thus, we can rewrite \( 25 + 45 \) as:
\[ 70 = 5(5 + 9) \]
So, the final answer would be:
\[ 5(5 + 9) \]