To find the enlarged length of the picture, we need to multiply the original length by the enlargement factor.
The original length is \( 4 \frac{1}{5} \) inches. We can convert this into an improper fraction:
\[ 4 \frac{1}{5} = \frac{21}{5} \]
Next, we multiply this by the enlargement factor of 7:
\[ \frac{21}{5} \times 7 = \frac{21 \times 7}{5} = \frac{147}{5} \]
Now, we convert \( \frac{147}{5} \) back into a mixed number. We divide 147 by 5:
\[ 147 \div 5 = 29 \text{ with a remainder of } 2 \]
This gives us:
\[ \frac{147}{5} = 29 \frac{2}{5} \]
Thus, the enlarged picture has a length of \( 29 \frac{2}{5} \) inches.
The correct answer is:
B. The enlarged picture has a length of 29 2/5 inches.