Examples with solutions for Area of a Rectangle: Using ratios for calculation

Exercise #1

The area of a rectangle is 50.

EB=15AB EB=\frac{1}{5}AB

EFBD EF\Vert BD

Work out the area of the rectangle EBFD.

505050AAABBBDDDCCCEEEFFF

Video Solution

Step-by-Step Solution

Since AB is 5 times larger than EB, the area of rectangle EBDF will be smaller than the area of rectangle ABCD accordingly

In other words, the ratio between the smaller rectangle to the larger one is 15 \frac{1}{5}

SABCD=5×SEBFD S_{\text{ABCD}}=5\times S_{EBFD}

Let's input the known data into the formula:

50=5×SEBFD 50=5\times S_{\text{EBFD}}

SEBFD=10 S_{\text{EBFD}}=10

Answer

10

Exercise #2

The area of the rectangle below is equal to 60.

EB=13AB EB=\frac{1}{3}AB

EFBD EF\Vert BD

Calculate the area of the smaller rectangle.

606060AAABBBDDDCCCEEEFFF

Video Solution

Step-by-Step Solution

Since AB is 3 times larger than EB, the area of rectangle EBDF will be smaller than the area of rectangle ABCD accordingly

In other words, the ratio between the smaller rectangle to the larger one is 13 \frac{1}{3}

SABCD=3×SEBFD S_{\text{ABCD}}=3\times S_{EBFD}

Let's input the known data into the formula:

60=3×SEBFD 60=3\times S_{\text{EBFD}}

SEBFD=20 S_{\text{EBFD}}=20

Answer

20

Exercise #3

The area of a rectangle is 36.

EB=16AB EB=\frac{1}{6}AB

EFBD EF\Vert BD

Calculate the area of rectangle EBFD.

363636AAABBBDDDCCCEEEFFF

Video Solution

Step-by-Step Solution

Since AB is 6 times larger than EB, the area of rectangle EBDF will be smaller than the area of rectangle ABCD accordingly

In other words, the ratio between the smaller rectangle to the larger one is 16 \frac{1}{6}

SABCD=6×SEBFD S_{\text{ABCD}}=6\times S_{EBFD}

Let's input the known data into the formula:

36=6×SEBFD 36=6\times S_{\text{EBFD}}

SEBFD=6 S_{\text{EBFD}}=6

Answer

6

Exercise #4

The area of the rectangle below is equal to 49.

EB=17AB EB=\frac{1}{7}AB

EFBD EF\Vert BD

Calculate the area of the rectangle EBFD.

494949AAABBBDDDCCCEEEFFF

Video Solution

Step-by-Step Solution

Since AB is 7 times larger than EB, the area of rectangle EBDF will be smaller than the area of rectangle ABCD accordingly

In other words, the ratio between the smaller rectangle to the larger one is 17 \frac{1}{7}

SABCD=7×SEBFD S_{\text{ABCD}}=7\times S_{EBFD}

Let's input the known data into the formula:

49=7×SEBFD 49=7\times S_{\text{EBFD}}

SEBFD=7 S_{\text{EBFD}}=7

Answer

7

Exercise #5

The area of the rectangle below is: 16.

EB=14AB EB=\frac{1}{4}AB

EFBD EF\Vert BD

Calculate the area of the rectangle EBFD.

161616AAABBBDDDCCCEEEFFF

Video Solution

Step-by-Step Solution

Since AB is 4 times larger than EB, the area of rectangle EBDF will be smaller than the area of rectangle ABCD accordingly

In other words, the ratio between the smaller rectangle and the larger one is 14 \frac{1}{4}

SABCD=4×SEBFD S_{\text{ABCD}}=4\times S_{EBFD}

Let's input the known data into the formula:

16=4×SEBFD 16=4\times S_{\text{EBFD}}

SEBFD=4 S_{\text{EBFD}}=4

Answer

4

Exercise #6

The area of a rectangle is 256 cm².

One side is 4 times longer than the other.

What are the dimensions of the rectangle?

Video Solution

Step-by-Step Solution

To find the area of the rectangle, we multiply the length by the width.

According to the data in the statement, one side will be equal to X and the other side will be equal to 4X

Now we replace the existing data:

S=x×4x S=x\times4x

256=4x2 256=4x^2

We divide the two sections by 4:

64=x2 64=x^2

We extract the square root:

x=64=8 x=\sqrt{64}=8

If we said that one side is equal to x and the other side is equal to 4x and we know that x=8

From here we can conclude that the sides of the rectangle are equal:

8,8×4=8,32 8,8\times4=8,32

Answer

8 x 32

Exercise #7

The rectangle ABCD is divided into the rectangle KBCM and the square AKMD.

The ratio between the rectangle and the square is 2:1.

The area of square AKMD is 16 cm².

Calculate the area of rectangle KBCM.

AAABBBCCCDDDKKKMMMS=18

Video Solution

Step-by-Step Solution

First we will divide the area of KBCM by the area of AKMD.

We know that their ratio is 2:1, therefore:

KBCMAKMD=21 \frac{KBCM}{AKMD}=\frac{2}{1}

We also know the area of AKMD, so we'll substitute it into the formula to obtain the following:

KBCM18=21 \frac{KBCM}{18}=\frac{2}{1}

Finally, we multiply by 18:

KBCM=2×18=36 KBCM=2\times18=36

Answer

32