How do you add a fraction to a decimal?

2 Answers
Apr 12, 2016

You need to convert them to similar format. Either both to decimal format or both to fractions.

Explanation:

There could be two ways of adding a fraction to a decimal.

(1) Convert fraction to the decimal format and add. If desired or required, the sum can again be converted into fraction.

(2) Convert the decimal to a fraction and then add two fractions together.

Apr 12, 2016

You need to either convert the decimal to a fraction or the fraction to a decimal.

Explanation:

Or at least that's the easiest way to go about adding a fraction to a decimal. For all intents and purposes (or porpoises) lets consider an example with fairly straight-forward numbers (no repeating decimals here). Lets say we wanted to add 1/5 and 0.50, that that would look like this:

1/5+0.50= ?

"Uhhhh... that doesn't look nice..."

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---------------------Converting to a decimal-----------------------

To convert a decimal to a fraction all we need to do is divide the numerator (top number) by the denominator* (bottom number). Like this:

1div5=0.2

Which, again, is the same as:

1/5=0.20

We know this because 5/5 equals 1. In fact any fraction that has the same number in the numerator and the denominator equals 1 because if you divide a number by itself the quotient (result of division) is 1. We can further prove that 1/5 is equal to 0.20 by adding 0.20 5 times in which case we get 1, just like this:

0.20+0.20+0.20+0.20+0.20= 1

So now that we know what both numbers are in decimal form we can add the two numbers, like so:

0.20+0.50= 0.70

---------------------Converting to a Fraction-----------------------

As I mentioned above we can also convert the decimal (0.50) to a fraction. Now we may know off the top of our heads that 0.50 equals 1/2, but we might not, this is not big deal because we can always add 50 plus 50 to get 100, like this:

50+50=100

This also means that:

0.50+0.50=1

Since it takes two 0.50's to equal 1 this means that 1 divided by 2 (or 1/2) is equal to 0.50, in equation form:

1/2= 0.50

Now that we know that 0.50 equals 1/2, we can set up our equation which looks like this:

1/5+1/2= ?

This is a little more tricky since we can't just add the two fractions, we have to find a common denominator. The easiest way to do this is to multiply the numerator and denominator of one by the denominator of the other, like so:

1/5*(2/2)=2/10

and

1/2*(5/5)=5/10

Now we can add both of these fractions together like this:

2/10+5/10=7/10

If we divide any number less than ten by 10 we get a decimal in this case if we divide 7 by 10 we get 0.70 since all we're really doing is moving the decimal point one place to the left. This can be expressed as an equation:

7div10=0.70

Surprise! We arrived at the same answer using two different methods!

I hope this helped!