TenMarks teaches you how to subtract fractions with like denominators.
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Learn about Subtracting Like Fractions In this lesson, let’s learn how to subtract like fractions. And the problem given to us is we need to subtract from 7/10, we need to subtract 3/10. How do we do this? What I'm going to do is do something interesting, I'm going to take—I'm actually going to take a sheet of paper or a strip. And we’re going to break it up into 10 pieces. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. So this is 1/10 of the strip, this is 1/10 of the strip and so on. This is also 1/10. Each one of these is 1/10 of a strip. So let’s say for example, the first one, I have 7/10. 1, 2, 3, 4, 5, 6, 7. So we’ve got seven of these pieces and what we’re going to do is take away 3/10 which means I'm going to take away three of these ten pieces. What am I left with? Well I'm left with 4/10 or 4 of the 1/10 pieces. So that’s how to do it diagrammatically. I can basically sketch it out and show out of seven pieces, I took away for. But there’s a way to do that using like fractions. As we can these are like fractions because their denominator is the same. So when the denominator is the same, and I have 7/10 and I want to subtract from it 3/10, the denominator gets copied so that remains the same. But I subtract the numerators, 7 and 3. So from 7 if I take away 3, I've got 4, which is 7-3. That’s what I put here. 7-3 gives me 4, so the answer is 4/10. What do we do? Copy the numerators, copy the denominators and it’s the same. And subtract the numerator. So what we’ll do is copy the denominator, and then subtract the numerator. Those are the things to remember. This only works if it’s a like fraction which means denominators are the same.