Janine wants to paint just the sides of a cylindrical pottery vase that has a height of 45 cm and a diameter of 14 cm. To the nearest whole number, find the

To find the lateral surface area of a cylinder, we can use the formula:

height*circumference

and to find the circumference, we can use:

diameter*pi                   ---Note: this could also be 2 times radius times pi. It's saying the same thing.

So really, our equation to find the lateral surface area of a cylinder is 

height*diameter*pi

Let's plug in our numbers:

45*14*3.14

1978.2

round up to a whole number

1978 cm

I'd use this method beause it's really simple to just plug in three numbers and solve the question. :)

$$\begin{array}{rll}
\\\mbox{Lateral area }&=&2\pi rh\\\\
&=& 2\pi \times7\times 45\\\\
&=& 1,979.203372\\\\
&=& 1,979\:\:cm^2 \mbox{ to the nearest square metre}
\end{array}$$

Ninja, you gave a great explanation as always but you forgot your units (2) and you were out by just a little because you did not use enough decimal places for pi.

Rounding errors always get compounded so you have to be careful not to round more than necessary until the very end.  

Thank You Both!

Ok, I see what I did wrong.

I assumed pi = 3.14, but really pi just keeps going forever with decimal digits.

Because everything is multiplied together, then rounded, my answer was one off.

Thanks Melody.