# Math algebra

posted by Cats24

It say to find the area of the irregular shape and it's a semi circle with the diameter of 5 and a square measure 8 and I got the area of the rectantagle which is 40 and now I got to find the area of the semi circle but it say the radius for the formula and I can't find get the rest but I need to explain my answer. A. 90.2cm squared B.241cm squared C.65.1cm squared D 72.3cm squared PLZ HELP!

1. Cats24

I ment I found the area of the rectangle I just need the semi circle and then add it up to find the amswe

2. Steve

A square of measure 8 does not have an area of 40.

A 5x8 rectangle has an area of 40.

You have a formula for the area of a circle, using its radius. Since the diameter is twice the radius,
πr^2 = π(d/2)^2 = πd^2/4

A circle of diameter d has area πd^2/4

you have a semicircle, so its area is πd^2/8 = 25π/8 = 9.82

40+25π/8 = 49.82

Hmmm. There must be something missing, since none of the answers comes even close.

Hmm -- maybe you do have a square of side 8.

64+25π/8 = 73.82

That looks close to D with a typo.

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