How do you type fractions into the calculator?
Write each fraction with a slash, like 3/4, and put the operation between them. Use + and − for adding and subtracting, * for multiplying, and / or ÷ for dividing.
For a mixed number, leave a space between the whole number and the fraction: 2 1/2 means two and one half. You can also mix in decimals, so 2/3 + 0.5 works and gives 7/6. The calculator follows order of operations, which means 1/2 + 1/3 * 3/4 multiplies first and returns 3/4.
Each answer comes with numbered steps. You'll see the common denominator it picked, the rewritten fractions, and the final reduction, so you can compare its work with yours line by line.
| You want | Type this | Answer |
|---|---|---|
| Add | 1/3 + 1/4 | 7/12 |
| Subtract | 3/4 − 1/6 | 7/12 |
| Multiply | 2/3 * 9/10 | 3/5 |
| Divide | 3/4 / 2/5 | 15/8 |
| Mixed numbers | 2 1/2 * 3/5 | 3/2 (1 1/2) |
How to add fractions with different denominators
You need a common denominator first, because you can only add pieces that are the same size. The least common denominator is the smallest number both denominators divide into.
Think of a pizza cut into thirds and another cut into fourths. You can't count one slice of each as two of anything, since the slices aren't the same size. Cutting both pizzas into twelfths fixes that, and then the slices can be counted together.
Here is 1/3 + 1/4 worked the same way the adding fractions calculator shows it:
Subtraction works the same way. For 3/4 − 1/6, the LCD is 12, so you get 9/12 − 2/12 = 7/12. Only the numerators change. The denominator tells you the size of each piece, and that size stays 12ths the whole time.
How do you find the least common denominator?
List multiples of the larger denominator until you reach one the smaller denominator divides into evenly. For 6 and 4, the multiples of 6 are 6, 12, 18, and 12 is the first one 4 goes into, so the LCD is 12.
You can also multiply the two denominators together. That always gives a common denominator, just not always the smallest. For 5/6 + 1/4, using 24 gives 20/24 + 6/24 = 26/24, which still reduces to 13/12. The answer is the same, but the numbers get bigger along the way. When the denominators are large, the LCM calculator finds the LCD for you.
How do you multiply fractions?
Multiply the numerators together and the denominators together, then simplify. You don't need a common denominator for multiplication.
This is the one operation where fractions are easier than they look. For 2/3 × 9/10, the top is 2 × 9 = 18 and the bottom is 3 × 10 = 30. That gives 18/30, which reduces to 3/5. The multiplying fractions calculator returns 3/5 directly. You can also cancel common factors before you multiply (the 3 and the 9, the 2 and the 10) to keep the numbers small.
How do you divide fractions?
To divide fractions, keep the first fraction, change ÷ to ×, and flip the second fraction. Teachers often call this keep, change, flip. Then multiply as usual.
Only the second fraction gets flipped. The first one stays exactly as it was. Flipping works because dividing by a number is the same as multiplying by its reciprocal. A quick check: 1/2 ÷ 1/4 asks how many quarters fit in a half, and the dividing fractions calculator gives 2.
How does the mixed number calculator handle whole numbers?
It turns every mixed number into an improper fraction first, does the math, and then shows the answer as a fraction, a mixed number, and a decimal. To convert by hand, multiply the whole number by the denominator and add the numerator.
Working with improper fractions avoids the borrowing and carrying that makes mixed number problems messy. You only switch back to a mixed number at the very end.
- Convert 2 1/2: 2 × 2 + 1 = 5, so 2 1/2 = 5/2.
- Multiply: 5/2 × 3/5 = 15/10.
- Simplify: 15/10 = 3/2.
- Write it as a mixed number: 3/2 = 1 1/2, or 1.5 as a decimal.
Mixed numbers in addition work the same way. For 1 3/4 + 2 2/3, the calculator rewrites them as 7/4 and 8/3 and uses 12 as the LCD. That gives 21/12 + 32/12 = 53/12, which is 4 5/12.
The decimal form is handy for checking whether an answer makes sense. 53/12 is 4.41666…, and 1 3/4 + 2 2/3 is roughly 1.75 + 2.67, so the result lands where you'd expect. When a decimal repeats, the fraction is the exact answer and the decimal is a rounded view of it.
How do you simplify a fraction?
Divide the numerator and the denominator by their greatest common factor. The value stays the same because you are dividing top and bottom by the same number.
If you type 12/18 on its own, the calculator works as a simplify fractions calculator and returns 2/3, since the GCF of 12 and 18 is 6. Every answer it gives is already in lowest terms. For larger numbers, the GCF calculator shows how the common factor is found.
A fraction is in simplest form when the numerator and denominator have no common factor other than 1. Most teachers expect final answers that way, and it also makes fractions much easier to compare.
What mistakes do people make with fractions?
The most common one is adding straight across: writing 1/3 + 1/4 = 2/7. Adding the denominators changes the size of the pieces, so the answer is wrong. You can tell 2/7 is off because it is smaller than 1/3, one of the numbers you started with.
When dividing, some people flip the first fraction instead of the second. Others multiply the parts of a mixed number separately. Always convert 2 1/2 to 5/2 before you multiply. With subtraction, watch the sign: 1/2 − 3/4 is −1/4, a negative number.
A last habit worth building is a quick size check. If you multiply by a fraction less than 1, the answer should shrink. If you divide by one, it should grow. That's why 3/4 ÷ 2/5 = 15/8 is bigger than 3/4.