Please help: If 1/2 inch is to 2 inches, what is [blank] to 30 inches?

[Ccorvair]

Please can you help me? I am not in school, I am just trying to find an answer for a project here's what I have, I am trying to scale up this : if 1/2 in. Is to 2 in. What is blank to 30 in. Thank you for your patients and you are welcome to use my question to promote children to stay in school.

 

[Dr.Peterson]

One way to think of "1/2 is to 2 as ___ is to 30" is that you want to multiply each first number by the same thing to get the second number.

What do you multiply 1/2 by, to get 2? One way or another, you should be able to see that the answer is 4: 1/2 multiplied by 4 is 2.

So ___, multiplied by 4, has to be 30. Can you fill in the blank?

There are several other ways you could do this; I can't be sure which way would fit you best without seeing an example of how you think.

 

[Otis]

Please can you help me? I am not in school, I am just trying to find an answer for a project … What is blank to 30 in …

Hello. That's 7.5 inches.

A ratio is a comparison of one number to another, like ½ to 2 and ? to 30. We can write such comparisons as fractions.

We want the fractions (½)/2 and ?/30 to equal one another because scaled comparisons are the same. We write the proportion:

\(\displaystyle \frac{½}{2} = \;\frac{?}{30}\)

As explained on this page, we find the unknown number by multiplying the two numbers on the diagonal (½×30) and dividing by the third number (2).

? = ½ × 30 ÷ 2 = 7½

?

 

[HallsofIvy]

Another way of thinking about it is that 4(1/2)= 4/2= 2. Since multiplying 1/2 by 4 is 2, dividing 2 by 4 is 1/2. 1/2 is 1/4 of 2. The what number is 1/4 of 30? 30/4= 15/2= 7.5.