To find the surface area of a rectangular prism, you use the formula:
Surface Area = 2lw + 2lh + 2wh
where l is the length, w is the width, and h is the height of the prism.
Let's break it down:
First, calculate the area of the two sides that are length by width:
lw = 3cm * 4cm = 12cm²
Since there are two such sides, multiply the area by 2:
2lw = 2 * 12cm² = 24cm²
Next, calculate the area of the two sides that are length by height:
lh = 3cm * 7cm = 21cm²
Again, since there are two such sides, multiply the area by 2:
2lh = 2 * 21cm² = 42cm²
Then, calculate the area of the two sides that are width by height:
wh = 4cm * 7cm = 28cm²
And as before, since there are two of these sides, multiply the area by 2:
2wh = 2 * 28cm² = 56cm²
Finally, add all the areas together to get the total surface area:
Surface Area = 2lw + 2lh + 2wh
Surface Area = 24cm² + 42cm² + 56cm²
Surface Area = 122cm²
Therefore, the correct answer is B. 122 cm².
