Question 22·Easy·Area and Volume
Rectangle has a length of and a width of . Rectangle is similar to rectangle , and the length of rectangle is times the length of rectangle . What is the area, in square centimeters, of rectangle ?
For similar-figure area problems, first identify the linear scale factor between the figures. Instead of recomputing all dimensions, remember that areas scale by the square of this factor: if side lengths are multiplied by , then areas are multiplied by . This lets you quickly find the new area by taking the original area and multiplying by , or, if needed, by scaling each dimension once and then using the standard area formula.
Hints
Use the scale factor correctly
You are told rectangle is similar to rectangle , and that the length of is times the length of . What does that tell you about how all side lengths change from to ?
Find both dimensions of rectangle Q
First, multiply the length of rectangle by to get the length of rectangle . Then do the same with the width of rectangle to get the width of rectangle .
Compute the area from the new dimensions
Once you know the new length and width of rectangle , use the area formula for a rectangle, , and then match your result to one of the answer choices.
Desmos Guide
Compute the scaled area directly
In Desmos, type the expression 6*4*(1.5)^2. The value that Desmos outputs is the area of rectangle ; compare that number to the answer choices given in the problem.
Step-by-step Explanation
Identify the given information
Rectangle has length and width . Rectangle is similar to rectangle , and the length of is times the length of .
That means the scale factor from rectangle to rectangle (for all side lengths) is .
Find the length of rectangle Q
The length of rectangle is . The length of rectangle is times this length:
So the length of rectangle is .
Find the width of rectangle Q using similarity
Because the rectangles are similar, every side of rectangle is multiplied by the same scale factor .
The width of rectangle is , so the width of rectangle is:
So the width of rectangle is .
Compute the area of rectangle Q and choose the answer
The area of a rectangle is .
For rectangle :
- Length
- Width
So the area is
The area of rectangle is square centimeters, which corresponds to answer choice C) 54.