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What is 87/100 - 1/8?

What is 87/100 - 1/8?

Here's how to subtract 1/8 from 87/100:

87
100
1
8

Step 1

We can't subtract two fractions with different denominators. So you need to get a common denominator. 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 87 by 8, and get 696.

Then we multiply 1 by 100, and get 100.

Next we give both terms new denominators -- 100 × 8 = 800.

So now our fractions look like this:

696
800
100
800

Step 2

Since our denominators match, we can subtract the numerators.

696 − 100 = 596

So the answer is:

596
800

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...

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

596
800
÷ 2 =
298
400

Let's try dividing by 2 again...

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

298
400
÷ 2 =
149
200

Let's try dividing by 2 again...

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

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...

Nope! So now we try the next greatest prime number, 41...

Nope! So now we try the next greatest prime number, 43...

Nope! So now we try the next greatest prime number, 47...

Nope! So now we try the next greatest prime number, 53...

Nope! So now we try the next greatest prime number, 59...

Nope! So now we try the next greatest prime number, 61...

Nope! So now we try the next greatest prime number, 67...

Nope! So now we try the next greatest prime number, 71...

Nope! So now we try the next greatest prime number, 73...

Nope! So now we try the next greatest prime number, 79...

Nope! So now we try the next greatest prime number, 83...

Nope! So now we try the next greatest prime number, 89...

Nope! So now we try the next greatest prime number, 97...

Nope! So now we try the next greatest prime number, 101...

Nope! So now we try the next greatest prime number, 103...

Nope! So now we try the next greatest prime number, 107...

Nope! So now we try the next greatest prime number, 109...

Nope! So now we try the next greatest prime number, 113...

Nope! So now we try the next greatest prime number, 127...

Nope! So now we try the next greatest prime number, 131...

Nope! So now we try the next greatest prime number, 137...

Nope! So now we try the next greatest prime number, 139...

Nope! So now we try the next greatest prime number, 149...

Nope! So now we try the next greatest prime number, 151...

No good. 151 is larger than 149. So we're done reducing.

There you have it! The final answer is:
87
100
1
8
=
149
200