A circle has a radius of 4cm. An isosceles triangle has a base of 8 cm and a height of 12 cm. Which shape has the greatest area?

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When reading a question try to pick out the important information, and don't get thrown off with unnecessary words like isosceles.

A circle has a radius of 4cm. An isosceles triangle has a base of 8 cm and a height of 12 cm. Which shape has the greatest area?

In this question you will need to work out areas of both a circle and a triangle and state which is larger. It is important to break the question down into smaller parts. Remember even if you cannot complete the whole question you can be awarded some marks for completing small parts.

1) Start with the easiest part: working out the area of the triangle.

Recall the formula for working out the area of the triangle: area=base*height/2

If you can’t remember the formula think of the area of a rectangle, and how a triangle is always half of the area of a rectangle with the same dimensions (try proving this with paper and scissors).

Area of triangle = 8cm*12cm/2 = 48cm^2

Remember that the units of area are squared and in this case are cm^2. There are usually marks awarded for units so make sure to include them.

2) Working out the area of the circle:

Recall the formula for working out the area of the circle: area=Pi*radius^2

Again if you find it difficult to remember formulae this one has an easy way to remember

Cherry pies delicious, apple pies are too

C=Pi*d, A=Pi*r^2

Here the area = 3.14*4cm*4cm = 50.24cm^2

Remember that the value of pi will be either given at the front of the paper or in the question, so if you are ever unsure on the number of a constant do look at the front of the paper.

3) Which has the greatest area?

Don’t forget to finish answering the question, you have done the hard part and it is often easy to forget to write the final answer before moving on to the next question especially under exam conditions. Always check at the end that you have answered the question that was posed, in this case:

The Circle.

Emma A. A Level Maths tutor, GCSE Maths tutor

About the author

is an online GCSE Maths tutor who has applied to tutor with MyTutor studying at Imperial College London University

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