area of this shape?

**andyboy179** · January 12th 2011, 12:35 PM

hi, i need to find the area of this shape:

for this would i do piex5x5=78.54
11x5=55
55+78.54=133.54???

if this is wrong could you please show me where im going wrong!

thanks!

**pickslides** · January 12th 2011, 12:44 PM

Hmmmm, a few questions.

Is 11 units the entire height or just that of the rectangle?

Do you know what shape the top section is?

**andyboy179** · January 12th 2011, 12:45 PM

just the rectangle is 11. not sure what shape the top section is, we were just told to copy it down how it was. kinda looks like a quarter of a circle?

**andyboy179** · January 12th 2011, 12:56 PM

if this is the case (refering to post 3) would this work:
piex5x5=78.54
11x5=55
55+78.54=133.54???

**pickslides** · January 12th 2011, 01:02 PM

Originally Posted by andyboy179

just the rectangle is 11. not sure what shape the top section is, we were just told to copy it down how it was. kinda looks like a quarter of a circle?

If it is a quarter circle then the area is $11\times 5 + 0.25\times \pi \times 5^2 = \dots$

If its a shape that "looks like" a quarter circle then the above calculation becomes an estimate of the area.

**andyboy179** · January 12th 2011, 01:10 PM

in my book last week for this question i wrote:
piexpiex5= 49.35/4=12.34
11x5=55
55+12.34= 67.34

and my teacher circled "piexpiex5" and wrote "Oh dead! what is going on here? piexpie??

does this mean i need to do piex5x5 or piex2x5?

**pickslides** · January 12th 2011, 01:17 PM

You need to do $\pi \times 5^2 = \pi \times 5\times 5$

Which is different to $\pi^2 \times 5 = \pi \times \pi \times 5 \approx 3.14 \times 3.14 \times 5$

and $\pi \times 2 \times 5 \approx 3.14 \times 2 \times 5$

can you see the differences...?

**e^(i*pi)** · January 12th 2011, 01:17 PM

You're only going to multiply by pi once since $A = \dfrac{\pi}{4} r^2$ . Its the radius squared, not pi squared.

If I can assume that top shape is 1/4 circle than the area of that bit is $A = \dfrac{\pi}{4} 5^2 = \dfrac{25\pi}{4}$

The total area is the area of the rectangle + area of the quarter circle

**andyboy179** · January 12th 2011, 01:23 PM

so if i were to do $\pi$ x5x5=78.54
78.54/4=19.64
11x5=55
19.64+55= 74.64

this would be correct?

**pickslides** · January 12th 2011, 01:29 PM

Looks good to me.

**bjhopper** · January 12th 2011, 02:47 PM

Hi,

The top section is not defined so I would assume that the answer would be in terms of an unknown quantity If the top section has a lenght of X and the circular section is a quarter circle an equation can be written.One thing is obvious i.e. the area must be less than 55

bjh

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