To calculate the amount of wrapping paper needed to wrap a rectangular box, we need to find the surface area of the box. The formula for the surface area \( S \) of a rectangular box is:
\[ S = 2(lb + lh + wh) \]
where:
- \( l \) is the length,
- \( w \) is the width,
- \( h \) is the height.
Given:
- Length \( l = 9 \) cm,
- Width \( w = 4 \) cm,
- Height \( h = 5 \) cm.
Now, we can substitute these values into the formula:
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Calculate each area component:
- \( lb = 9 \times 4 = 36 \) cm²
- \( lh = 9 \times 5 = 45 \) cm²
- \( wh = 4 \times 5 = 20 \) cm²
-
Add these areas:
- \( lb + lh + wh = 36 + 45 + 20 = 101 \) cm²
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Now multiply by 2:
- \( S = 2 \times 101 = 202 \) cm²
Therefore, the amount of wrapping paper needed to wrap the gift is 202 cm².