Question
A rectangular strip $25\ cm × 7\ cm$ is rotated about the longer side. Find The total surface area of the solid thus generated.
✓
Answer
Since the rectangular strip of $25\ cm × 7\ cm$ is rotated about the longer side, we have:
Height, $h = 25\ cm$
Radius, $r = 7\ cm$
$\therefore$ Total surface area $=2\pi\text{r}(\text{r}+\text{h})=2\pi(7)(25+7)$
$=14\pi\ (32)$
$=448\pi\ \text{cm}^2$
$448\times\frac{22}{7}\text{cm}^2$
$=1408\text{cm}^2$
Height, $h = 25\ cm$
Radius, $r = 7\ cm$
$\therefore$ Total surface area $=2\pi\text{r}(\text{r}+\text{h})=2\pi(7)(25+7)$
$=14\pi\ (32)$
$=448\pi\ \text{cm}^2$
$448\times\frac{22}{7}\text{cm}^2$
$=1408\text{cm}^2$
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