IXL | Perimeter and area: effect of changing the side length

Look at this rectangle:

6 m

5 m

If both dimensions are doubled, then which of the following statements about its area will be true?

The new area will be

times the old area.

The new area will be

of the old area.

The new area will be

times the old area.

The new area will be

times the old area.

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Learn with an example

question

Look at this rectangle:

6 yd

8 yd

If both dimensions are tripled, then which of the following statements about its area will be true?

The new area will be

times the old area.

The new area will be

times the old area.

The new area will be

times the old area.

The new area will be

times the old area.

solution

You can solve this problem without using the measurements given in the diagram.

The original rectangle had this area:

A = bh

The new rectangle will have 3 times the base and 3 times the height. Since the original dimensions were b and h, the new dimensions will be 3b and 3h. Calculate the area:

A	=	(3b)(3h)

	=	9bh

Divide the new area by the original area and simplify.

new area

original area

9bh

The new area will be

times the old area.

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