David Marain over at MathNotations has been periodically tweeting an SAT problem of the day via @dmarain. A recent series of tweets asked:
A 42 oz mix of nuts is 6 parts peanuts to 1 part cashews. How many ounces of cashews must be added to make a make the mixture 2 parts cashews to 1 part peanuts? Does Singapore (bar) model method work here?
Sure it can! Here’s one solution.
First model the beginning mixture at 6:1.
Next, we can figure out how many units need to be added to the cashews to make the cashews to peanuts ratio 2:1.
Since there are 11 additional units and the value of each unit is 6 oz, we can find the value of the added cashews.
66 ounces of cashews must be added to the peanuts to make the mixture 2:1.
Changing Ratios is taught in level 6A in the Primary Mathematics materials (U.S. Edition), typically used in 6th grade classrooms.
About Cassy Turner
Thanks, Cassy
One good model diagram truly is worth a thousand words! My question was rhetorical. I was hoping someone like you would run with it. What do you find is the most difficult obstacle in training? Asking adults to think “different”? Developing an understanding of “unit”? Resistance to change? I would think the proof is in how their students would react…
Dave