IXL | Perimeter and area: changes in scale

Look at this rectangle:

10 yd

5 yd

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

The new perimeter will be

times the old perimeter.

The new perimeter will be

of the old perimeter.

The new perimeter will be

times the old perimeter.

The new perimeter will be

times the old perimeter.

ref_doc_title.

Learn with an example

question

Look at this rectangle:

5 in

8 in

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

The new perimeter will be

times the old perimeter.

The new perimeter will be

of the old perimeter.

The new perimeter will be

times the old perimeter.

The new perimeter will be

times the old perimeter.

solution

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

The original rectangle had this perimeter:

P = 2(b + h)

The new rectangle will have 2 times the base and 2 times the height. Since the original dimensions were b and h, the new dimensions will be 2b and 2h. Calculate the perimeter:

P	=	2(2b + 2h)

	=	2 · 2(b + h)

	=	4(b + h)

Divide the new perimeter by the original perimeter and simplify.

new perimeter

original perimeter

4(b + h)

2(b + h)

The new perimeter will be

times the old perimeter.

Looking for more? Try these:

Lesson: Area of circles

Lesson: Perimeter

Lesson: Area of parallelograms

$Confetti$

Excellent!

Now entering the Challenge Zone—are you ready?

Questions
answeredQuestions

Time
elapsedTime

hr	min	sec
00	00	04

SmartScore
out of 100
IXL's SmartScore is a dynamic measure of progress towards mastery, rather than a percentage grade. It tracks your skill level as you tackle progressively more difficult questions. Consistently answer questions correctly to reach excellence (90), or conquer the Challenge Zone to achieve mastery (100)! Learn more

Teacher tools

Work it out

Not feeling ready yet? These can help:

V.1Perimeter

V.2Area

BB.6Area of circles

BB.5Circumference of circles

L.1Understanding ratios

Lesson: Area of circles

Lesson: Perimeter

Lesson: Area of parallelograms

Excellent! You got that right!

Jumping to level 1 of 1

Excellent!