## Common Ratio Formula

A relation is getting form the comparison of two quantities like in some wisdom is called a common ratio. Common ratio will be show by the terms of fraction, that is, a:b is equal to `a/b` For example 25 is `1/4` of the hundred, Therefore, the ratio of 25 to 100 is `1/4` . We can write it in ratio as 1:4.

If 19 pounds of pizza cost $15, calculate the common ratio for 26 pounds of pizza by using formula.

Solution:

19 pounds of pizza cost is $15 is expressed in common ratio format as 19: 15. This can be written in fraction format as `19/15` . Therefore,

`19/15` = `26/x`

Now we have to do the cross multiplication. Therefore we get

19 `xx` x = 26 `xx` 15

19x = 390

Now we have to divide both sides by 19. Therefore we get

`(19x)/19` = `390/19`

x = 20.53

Therefore, the cost of 26 pounds of pizza is $20.53

If 20 pounds of flowers cost is $16, calculate the common ratio for 27 pounds of flowers by using formula.

Solution:

20 pounds of flowers cost $16 is expressed in common ratio format as 20: 16. This can be written in fraction format as `20/16` . Therefore,

`20/16` = `27/x`

Now we have to do the cross multiplication. Therefore we get

20 `xx` x = 27 `xx` 16

20x = 432

Now we have to divide both sides by 20. Therefore we get

`(20x)/20` = `432/20`

x = 21.6

Therefore, the cost of 27 pounds of flowers is $21.6

If 21 pounds of pizza cost is $17, calculate the common ratio for 28 pounds of pizza by using formula.

Solution: Therefore, the cost of 28 pounds of flowers is $22.67

If 22 pounds of flowers cost is $18, calculate the common ratio for 29 pounds of flowers by using formula.

Solution: Therefore, the cost of 29 pounds of flowers is $23.72

**Examples for common ratio formula:**

Example 1:Example 1:

If 19 pounds of pizza cost $15, calculate the common ratio for 26 pounds of pizza by using formula.

Solution:

19 pounds of pizza cost is $15 is expressed in common ratio format as 19: 15. This can be written in fraction format as `19/15` . Therefore,

`19/15` = `26/x`

Now we have to do the cross multiplication. Therefore we get

19 `xx` x = 26 `xx` 15

19x = 390

Now we have to divide both sides by 19. Therefore we get

`(19x)/19` = `390/19`

x = 20.53

Therefore, the cost of 26 pounds of pizza is $20.53

**Example 2:**If 20 pounds of flowers cost is $16, calculate the common ratio for 27 pounds of flowers by using formula.

Solution:

20 pounds of flowers cost $16 is expressed in common ratio format as 20: 16. This can be written in fraction format as `20/16` . Therefore,

`20/16` = `27/x`

Now we have to do the cross multiplication. Therefore we get

20 `xx` x = 27 `xx` 16

20x = 432

Now we have to divide both sides by 20. Therefore we get

`(20x)/20` = `432/20`

x = 21.6

Therefore, the cost of 27 pounds of flowers is $21.6

**Practice problems for common ratio formula:**

Problem 1:Problem 1:

If 21 pounds of pizza cost is $17, calculate the common ratio for 28 pounds of pizza by using formula.

Solution: Therefore, the cost of 28 pounds of flowers is $22.67

**Problem 2:**If 22 pounds of flowers cost is $18, calculate the common ratio for 29 pounds of flowers by using formula.

Solution: Therefore, the cost of 29 pounds of flowers is $23.72