Question

The thickness of a hollow wooden cylinder is 2 cm. It is 35 cm long and its inner radius is 12 cm. Find

the volume of wood used to make the cylinder.

Answer 1

The volume of the wood pipe is
OUTER VOLUME - INNER VOLUME

OUTER VOLUME is
$\pi{r}^{2} h$
here radius is 2+12: 14cm

Inner volume is
$\pi {r}^{2} h$
here radius is 12 cm
In both the cases the height remains the same
So the volume is


$\pi{h}{(r + r)}{(r - r)}$
So
$(22 \div 7) \times 35 \times (14 - 12)(14 \times 12) = 13650 {cm}^{3}$

Answer 2

AnsWer:

We have,

r = Inner radius of the cylinder = 12 cm

Thickness of the cylinder = 2cm

$\therefore$ R = outer radius of the cylinder = (12+2) cm = 14cm

h = Height of the cylinder = 35cm

__________________________

$\therefore$ Volume of the wood = π (R² - r²) h

$→ \sf\frac{22}{7} \times {(14)}^{2} - {(12)}^{2} \times 35 \: {cm}^{3} \\ \\ → \sf \frac{22}{7} \times (14 + 12) \times (14 - 12) \times 35 \: {cm}^{3} \\ \\ →\sf \: 22 \times 26 \times 2 \times 5 \: {cm}^{3}= 5720 \: {cm}^{3}$