math help

What is 72/63 + 4/5?

What is 72/63 + 4/5?

Here's how we add

72
63
+
4
5

Step 1

We can't add two fractions with different denominators (the bottom number). So you need to get a common denominator - both bottom numbers need to match. To do this, you'll multiply the denominators times each other... but the numerators have to change, too. They get multiplied by the other term's denominator.

So we multiply 72 by 5, and get 360, then we multiply 63 by 5 and get 315.

72/63 times 5

Do the same for the second term. We multiply 4 by 63, and get 252, then multiply 63 by 5 and get 315.

4/5 times 63

So now our fractions look like this:

360
315
+
252
315

Step 2

Since our denominators match, we can add the numerators.

360 + 252 = 612

So the answer is:

612
315

Step 3

Last of all, we need to simplify the fraction, if possible. Can it be reduced to a simpler fraction?

To find out, we try dividing it by 2...

Nope! So now we try the next greatest prime number, 3...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

612
315
÷ 3 =
204
105

Let's try dividing by that again...

Are both the numerator and the denominator evenly divisible by 3? Yes! So we reduce it:

204
105
÷ 3 =
68
35

Let's try dividing by that again...

Nope! So now we try the next greatest prime number, 5...

Nope! So now we try the next greatest prime number, 7...

Nope! So now we try the next greatest prime number, 11...

Nope! So now we try the next greatest prime number, 13...

Nope! So now we try the next greatest prime number, 17...

Nope! So now we try the next greatest prime number, 19...

Nope! So now we try the next greatest prime number, 23...

Nope! So now we try the next greatest prime number, 29...

Nope! So now we try the next greatest prime number, 31...

Nope! So now we try the next greatest prime number, 37...

No good. 37 is larger than 35. So we're done reducing.

There you have it! Here's the final answer to 72/63 + 4/5

72
63
+
4
5
=
68
35
© 2014 Randy Tayler