Multiplying Fractions and Mixed Numbers
19 November 2009
Its back! Yayyyy!!!
So…I am currently teaching multiplying fractions and mixed numbers to my upper level sixth graders. We teach how to multiply fractions with a Hershey chocolate bar, and we teach how to multiply mixed numbers with a cookie recipe that we enlarge 2 1/2 times. They actually bring the ingredients and we mix it up and I bring them cookies the next day. (I do not deserve credit for thinking of this, the teachers at my school did this before I got there.) So here are some problems for you…
1. 3/4 x 5/6 =
Get the answer and also tell me if you remembered anything special you could do to make it easier.
2. 5 1/3 x 7 1/2 =
Get the answer and tell me how you did it.
Ok, so you multiple the tops across and the bottoms across so – 15/24 simplified = 5/8
And the other one, you get them both in fraction form and do the same thing – 240/6 simplified =40!
Do I win?
5/8: numerator of first and denominator of second could be reduced (both divided by 3), so 3/4 x 5/6 became 1/4 x 5/2. Then multiply across (1×5 and 4×2) and you get 5/8. Do it the long way and get 15/24, then reduce down (divide by common number of 3) and get 5/8.
40: 5 1/3 equals 16/3. 7 1/2 equals 15/2. 16/3 x 15/2. Use the same process as the first to reduce down: 8/1 x 5/1…or 8 x 5. Equals 40.
Took me a minute to remember what to do, and I’m sure I don’t have the terminology right! Yay for the return of AYSTASG!
i would like to be smarter than a sixth grader.
1) 3/4 x 5/6 = 3×5 / 4×6 = 15/24 = 5/8
2) 5 1/3 x 7 1/2 = 16/3 x 15/2 = 240/6 = 40
Great answers!