Chez J Posted April 1, 2011 Share Posted April 1, 2011 We are working on mixed numbers and improper fractions. We worked the problem 3 1/2 to convert to an improper fraction. After showing my dd to multiply the whole number by the denominator and then add the numerator, she wrote this... 3 1/2 = 3x2+1 So I had her remember the order of operations and to put in the parentheses so it is... 3 1/2 = (3x2)+1 = 7/2 So, my question is...we lost the denominator during the conversion part. Meaning, it only shows up again in the answer. Would it be correct to write... (3x2)+1 = 7/2 2 Quote Link to comment Share on other sites More sharing options...
Dana Posted April 1, 2011 Share Posted April 1, 2011 So, my question is...we lost the denominator during the conversion part. Meaning, it only shows up again in the answer. Would it be correct to write... (3x2)+1 = 7/2 2 Yes, this is correct. What's really going on with the conversion between mixed numbers and rational numbers is you're doing addition. 3 1/2 means 3 + 1/2 (a useful thing to be aware of when dividing polynomials). So 3 + 1/2 requires a common denominator: 2 (3/1)(2/2) + (1/2) [getting the common den] and this is what leads you to your final note: (3*2 + 1) / 2 I think I'll be having my son really work the conversion as addition until he's begging for the shortcut. It's how we did long division (pull out the manipulatives and work it... now you can write it). :D Quote Link to comment Share on other sites More sharing options...
Chez J Posted April 1, 2011 Author Share Posted April 1, 2011 Yes, this is correct. What's really going on with the conversion between mixed numbers and rational numbers is you're doing addition. 3 1/2 means 3 + 1/2 (a useful thing to be aware of when dividing polynomials). So 3 + 1/2 requires a common denominator: 2 (3/1)(2/2) + (1/2) [getting the common den] and this is what leads you to your final note: (3*2 + 1) / 2 I think I'll be having my son really work the conversion as addition until he's begging for the shortcut. It's how we did long division (pull out the manipulatives and work it... now you can write it). :D Thank you! That was how I showed her - adding the whole numbers. But, then went to the short cut. I thought the denominator was right in that equation, but I didn't want to mess up anything for pre-algebra. :) Quote Link to comment Share on other sites More sharing options...
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