Question

When you convert feet to inches, how do you decide which part of the conversion factor should be in the numerator and which in the denominator?

Answer 1

Solution

So in this problem we have to convert $\text{feet}$ to$\text{inches}$. In general, when you have to convert one unit to another, you have make sure that the unit you $\text{want to convert to}$ is in $\text{numerator}$. So in this case $\text{inches}$ would be in the $\text{numerator.}$ To make it easier to understand why, let`s solve an example.

Let`s say we have to turn 6 feet to inches. The math would look like this:

1 foot = 12 inches (first we have to have a conversion factor,since we have to convert feet to inches, we divide by 1 foot)

$\genfrac{}{}{0ex}{}{1foot}{1foot}$ = $\genfrac{}{}{0ex}{}{12inches}{1foot}$

$1=\genfrac{}{}{0ex}{}{12inches}{1foot}$ ->and now we have general conversion factor.

Now we just $\text{enter the value}$. In this case 6 feet.

$\text{Distance value in inches}$ = 6 feet *$\genfrac{}{}{0ex}{}{12inches}{1foot}$

So foot and feet cancel each other and we get the final value of $\text{72 inches.}$

We can see if the unit we wanted to convert to were to be in the determinator, it would be cancelled.

Therefore, 

So in this problem we have to convert $\text{feet}$ to $\text{inches}$. In general, when you have to convert one unit to another, you have make sure that the unit you $\text{want to convert to}$ is in $\text{numerator}$. So in this case $\text{inches}$ would be in the $\text{numerator.}$