a circle has an area of 78mm^2. find its diameter

Question

saifoo.khan · Answer

use the formula, insert the values and Bingo!

saifoo.khan · Answer

try it..

anonymous · Answer

$$\pi (r)^2 = 78$$

anonymous · Answer

Remember the formula A=(pi)r^2. Well you want to find the diameter d which is related to r by: d=2r. Therefore r = d/2. Substitute this into the Area formula for r to get:

A = (pi)(d/2)^2 = (pi)d^2/4. Now rearrange this to get d in terms of A and pi:

d = [4A/(pi)]^(1/2)  and take the positive root.

anonymous · Answer

Now just plug in your value for A to get the diameter in mm^2

anonymous · Answer

this formula is complicated can you write in a simple way

anonymous · Answer

$$A = \pi (d/2)^2 = \pi d^2 / 4$$

anonymous · Answer

Next I just re-arranged to find $$d $$ in terms of $$\pi $$. You do this by writing:

anonymous · Answer

$$d = [4A/(\pi)]^{1/2}  = \sqrt{4A/(\pi)}$$

anonymous · Answer

can you check I got 25.8 is that right

anonymous · Answer

24