math help

What is 9/10 + 7/8?

What is 9/10 + 7/8?

This is how to add

9
10
+
7
8

Step 1

Of course, you can't add two fractions if the denominators (bottom numbers) don't match. To get a common denominator, multiply the denominators together. Then we fix the numerators by multiplying each one by their other term's denominator.

Now you multiply 9 by 8, and get 72, then we multiply 10 by 8 and get 80.

9/10 times 8

Do the same for the second term. We multiply 7 by 10, and get 70, then multiply 10 by 8 and get 80.

7/8 times 10

The problem now has new fractions to add:

72
80
+
70
80

Step 2

Since our denominators match, we can add the numerators.

72 + 70 = 142

This yields the answer

142
80

Step 3

The last step is to reduce the fraction if we can.

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

Are both the numerator and the denominator evenly divisible by 2? Yes! So we reduce it:

142
80
÷ 2 =
71
40

Now, try the same number again.

Nope. Try the next prime number, 3...

Nope. Try the next prime number, 5...

Nope. Try the next prime number, 7...

Nope. Try the next prime number, 11...

Nope. Try the next prime number, 13...

Nope. Try the next prime number, 17...

Nope. Try the next prime number, 19...

Nope. Try the next prime number, 23...

Nope. Try the next prime number, 29...

Nope. Try the next prime number, 31...

Nope. Try the next prime number, 37...

Nope. Try the next prime number, 41...

No good. 41 is larger than 40. So we're done reducing.

Congratulations! Here's your final answer to 9/10 + 7/8

9
10
+
7
8
=
71
40
© 2014 Randy Tayler