a pen stand is cylinderircal in shape with the radius 3.5cm and height 10.5cm. how much cardboard will be required to make 25 such pen stand and what will be the volume of 1 pen stand

Answer:
Radius of pencil holder = 3.5 cm 
Height of pencil holder = 10.5 cm
We know pencil stand have open top : So the surface area of pencil holder
= Areas of bottom circles + Area of the side
= $\mathrm{\pi } {\mathrm{r}}^{ 2} + 2 \mathrm{\pi } \mathrm{r} \mathrm{h}$
So, cardboard used in one pencil holder = surface area of pencil holder

= $\frac{22}{7}{\left( 3.5 \right)}^2 + 2 \frac{22}{7} \left( 3. 5\right) \left( 10.5 \right)$

= 38.5 + 231

= 269.5 $c{m}^2$
So cardboard used in 25 pen holder is

= 25 $\times$ 269.5 

=  6737.5 $c{m}^2$                                   ( Ans )

Volume of one pen stand = $\mathrm{\pi } {\mathrm{r}}^2 \mathrm{h}$

= $\frac{22}{7}{\left( 3.5 \right)}^2 \left( 10.5 \right)$

= 404.25    $c{m}^3$                                ( Ans )