Maths Homework - could someone please help with finding area and perimeter of odd shapes

[yohoohoo]

DD having a meltdown with this homework on area and perimeter. Really struggling to do this

Well the circle - calc the area as if it's a proper circle then multiply by 0.75

Same for perimeter - calc as normal, remove one quarter and then add the two square sides

Find the perimeter of the circle using formula.
Divide by four.
Minus one part.
Add on ten ( the straight bits)

2.calculate rectangle.
Minus one end
Calculate cycle and half.
Add half and rectangle.

Circle picture:

Radius is 5cm. Area of whole circle is pi times radius squared. Multiply this by 3/4 or 0.75 to get area.

Perimeter: perimeter of whole circle is 2 times pi times radius. Multiply this by 3/4 or 0.75. You must also add 5cm twice, because the two straight lines are part of the perimeter.

The other can be calc as if it's a rectangle, having removed the 3cm radius semi circle first, and then add on the semi circle

If it is to scale you could get your DD a piece of string to measure the perimeter with a ruler and that might help her understand a bit better.

Area of shape one is , assuming the chunk taken out 90o angle at centre , 3/4 of the area of the circle. likewise perimeter will be 3/4 of the circumference + the 5cm radius x 2

The second one will be the area of the rectangle plus area of semi circle , perimeter is 2 long sidesof rectangle + one short and half the circumference of the circle.

So a rectangle of 22 x 9 and a 3cm semi circle

Radius of semicircle in the rectangle question is not 3cm; it is 4.5cm.

Of course sorry

I was talking about these today with my ds.
I think you need to be able to see

1. whole circle - 1/4 of circle.
2. rectangle + semi circle.

Once you get a hang of it it will get easy, if you know the formula for calculating areas of different shapes.

I think it would help to check your son's basics are secure like fractions and individual shaped area calculations like just circle and just square. Find half a square. Find 3/4 a square. Ensure he understands decimal equivalent of fractions. Once all the basic elements are secure this would be much easier for him. I would definitely check for gaps in his maths first.