GCSE maths homework help (URGENT)

How am i supposed to do q 4? http://prntscr.com/3s7nvb I need to know asap

aliciaa1997

So you find the area of the whole shape which is 90/360 x pi x r^2 = 90/360 pi x 64 = 16 pi

then you find the area of the triangle which is half base x height= 4 x 8= 32

Then you subtract the area of the triangle from the area of the whole shape = 16 pi - 32 = 18.27cm^2

I think that's right

(edited 9 years ago)

Reply 2

Parallex

Area of the sector = (pi*8*8)/4
= 50.26cm^2.

Minus the area of the triangle...
Right angled triangle = 1/2*b*h
= 0.5 * 64 = 32cm^2.

50.26-32 = 18.26cm^2.

Reply 3

SidTheSloth1

Thanks for the reply but I still dont really understand, how do you know how to find the area of the sector?

Reply 4

gdunne42

Original post by SidTheSloth1

Thanks for the reply but I still dont really understand, how do you know how to find the area of the sector?

It's a fraction of a circle. What fraction of a full circle is it?

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Reply 5

Madmatician

Original post by SidTheSloth1

Thanks for the reply but I still dont really understand, how do you know how to find the area of the sector?

Area of full circle: pi x r^2

To find the area of a sector, you find the area of the full circle, then multiply it by the fraction of the circle that the sector represents

So in Question 4, the angle of the sector is a right-angle, therefore we know it's 90 degrees

We can thus workout that the sector represents 1/4 of the full circle because the angle of the sector is 90 degrees out of 360 degrees. 90/360 can be simplified to 1/4

So then you work out the area of the full circle and multiply it by 1/4 to get the area of that particular sector

So the area would be (pi x 8^2) x 1/4

Conversely, you could divide the area of the full circle by 4 to get 1/4 of the area. Either way, you'll end up with the same answer.

Hope I've helped.

Sorry if it's a bit repetitive or confusing - I'm not the best at explaining :redface: