math help

What is 72/63 + 7/10?

What is 72/63 + 7/10?

Here's how you add

72
63
+
7
10

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 10, and get 720, then we multiply 63 by 10 and get 630.

72/63 times 10

Do the same for the second term. We multiply 7 by 63, and get 441, then multiply 63 by 10 and get 630.

7/10 times 63

So now our fractions look like this:

720
630
+
441
630

Step 2

Since our denominators match, we can add the numerators.

720 + 441 = 1161

So the answer is:

1161
630

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...

No good. So next you try the next prime number, which is 3...

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

1161
630
÷ 3 =
387
210

So far so good... let's try to divide by that number again.

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

387
210
÷ 3 =
129
70

So far so good... let's try to divide by that number again.

No good. So next you try the next prime number, which is 5...

No good. So next you try the next prime number, which is 7...

No good. So next you try the next prime number, which is 11...

No good. So next you try the next prime number, which is 13...

No good. So next you try the next prime number, which is 17...

No good. So next you try the next prime number, which is 19...

No good. So next you try the next prime number, which is 23...

No good. So next you try the next prime number, which is 29...

No good. So next you try the next prime number, which is 31...

No good. So next you try the next prime number, which is 37...

No good. So next you try the next prime number, which is 41...

No good. So next you try the next prime number, which is 43...

No good. So next you try the next prime number, which is 47...

No good. So next you try the next prime number, which is 53...

No good. So next you try the next prime number, which is 59...

No good. So next you try the next prime number, which is 61...

No good. So next you try the next prime number, which is 67...

No good. So next you try the next prime number, which is 71...

No good. 71 is larger than 70. So we're done reducing.

And we're done! Here's the final answer to 72/63 + 7/10

72
63
+
7
10
=
129
70
© 2014 Randy Tayler