# Thread: Volume and areas of prisms

1. ## Volume and areas of prisms

Hi all

I have come across the question below , I get the basics of calculating the figures but the "surd form" has thrown me. Can anyone show and explain how to do this?

2. ## Re: Volume and areas of prisms

i. application of Pythagoras ...
$|MB|=\sqrt{30^2-10^2} = \sqrt{800} = 20\sqrt{2} \, cm$ ... the length of MB, the height of triangle ABC, is in "surd" form.

Now that you have that necessary piece of information, give the remainder of these questions a go.

3. ## Re: Volume and areas of prisms

Thanks Skeeter

I have took that and still cant seem to get anywhere with the following questions

4. ## Re: Volume and areas of prisms

Originally Posted by trev2304
Thanks Skeeter

I have took that and still cant seem to get anywhere with the following questions
You're telling me you cannot find the area of the triangular base, part (ii)? ... you need to have a face-to-face session with your instructor.

5. ## Re: Volume and areas of prisms

i know how to find the area of the base, just not how to do it in surd form. I don't have an instructor as I am teaching myself in preparation for starting a uni course next year

6. ## Re: Volume and areas of prisms

base area = $\dfrac{b \cdot h}{2} = \dfrac{20 \cdot 20\sqrt{2}}{2} = 200\sqrt{2} \, \, cm^2$

recommend you learn some arithmetic with radicals ...