Equivalent FractionsDate: 05/07/99 at 07:30:01 From: Sam Subject: Math (equivalent fractions) I am trying to understand equivalent fractions. Example: 6 1 -- = - 12 2 Date: 05/07/99 at 11:49:09 From: Doctor Rick Subject: Re: Math (equivalent fractions) Hi, Sam. This is 6/12: +---+---+---+---+---+---+ |xxx|xxx|xxx|xxx|xxx|xxx| |xxx|xxx|xxx|xxx|xxx|xxx| +---+---+---+---+---+---+ | | | | | | | | | | | | | | +---+---+---+---+---+---+ The big rectangle is cut into 12 equal-sized boxes, and 6 are marked with x's. Each box is 1/12 of the whole, so 6 of them is 6/12. This is 1/2: +-----------------------+ |xxxxxxxxxxxxxxxxxxxxxxx| |xxxxxxxxxxxxxxxxxxxxxxx| +-----------------------+ | | | | +-----------------------+ The big rectangle is cut into 2 equal-sized boxes, and 1 is marked with x's. Each box is 1/2 of the whole. Both pictures show the same space marked with x's. You could imagine the rectangle being a chocolate cake. If you cut it in 2 equal-sized pieces and eat one, you have eaten the same amount as if you cut it in 12 equal-size pieces and ate 6 of them. The two fractions are EQUIVALENT. How do you find equivalent fractions? Look again at that cake cut into two pieces. Make 5 vertical cuts, and you have cut the cake into 12 pieces. You multiplied the total number of pieces by 6, but you also multiplied the number of pieces you're going to eat by 6. The total number of pieces is the denominator. The number of pieces you chose is the numerator. You just multiplied the numerator and the denominator by the same number, 6. You could have made any number of vertical cuts and you'd get another fraction equivalent to 1/2. If you multiply both the numerator and the denominator by the same number - any whole number - you will get a fraction equivalent to 1/2. For instance, you can multiply by 2/2 to get 2/4; by 3/3 to get 3/6; by 4/4 to get 4/8, and so on. What about going the other way? Starting with 6/12, you can find some equivalent fractions by DIVIDING the numerator and denominator by the same number. But you can't just pick any number, as you can when you multiply. The numerator and denominator must both be DIVISIBLE by the number. Both 6 and 12 are divisible by 2, so one fraction equivalent to 6/12 is 3/6 (divide 6 by 2 and divide 12 by 2). Both 6 and 12 are divisible by 3, so another equivalent fraction is 2/4. Both 6 and 12 are divisible by 12, so another equivalent fraction is 1/2. But 1 and 2 have no common factors, so you cannot find a fraction equivalent to 1/2 by dividing. There is no equivalent fraction with smaller numbers. We say that 1/2 is IN LOWEST TERMS. Remember I said that 4/8 is equivalent to 1/2? Two fractions that are equivalent to the same fraction are equivalent to each other. This means that 4/8 and 6/12 are equivalent. But 6 is not a multiple of 4, and 12 is not a multiple of 8. So what's the rule? If you want to find ALL the fractions that are equivalent to 6/12, first reduce it to lowest terms: find the equivalent fraction that is in lowest terms. That's 1/2. Then multiply the numerator and denominator by each number, 1, 2, 3, 4, and so on, and you will have a list of ALL the fractions equivalent to 6/12. The list will go on forever, so don't try to write them all - but you know what they are. I've probably said more than you wanted to see. I hope it helps. If you have specific problems that you can't do, let us know - and tell us your wrong answer, that will help us figure out what you need to learn. - Doctor Rick, The Math Forum http://mathforum.org/dr.math/ |
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