I am not a math genius...I wish I were. I use Excel a lot and that plus logic gets me by. But this makes NO sense to me. How did they come up with the last step - the $10 + $10 ?? Why did they have to add up to $38 to figure out the change of 12.40?
Seems to me it’s much easier to do it the regular way - .40 to make it to 8.00 and 12.00 to get from 8.00 to 20.00
You, sir, are much more qualified to teach math than those common core idiots.
No use trying to understand the convoluted logic of these science dropouts. There is a reason they are in “education” vs something useful. (No insult meant to real teachers, who are invaluable.)
That’s the way I was taught to make change at a register that didn’t calculate it. Count the coins to get to the next whole dollar (40 cents to make 8 dollars). Then count ones to get to the next multiple of 5 (2 dollars to make 10 dollars) and then the rest (and 10 to make 20). I hated customers who gave me strange amounts of change to make it “easy” or to avoid getting pennies back.
“Seems to me it’s much easier to do it the regular way - .40 to make it to 8.00 and 12.00 to get from 8.00 to 20.00”
That’s what they’re doing: how many units it takes to get to the next unit; for money, units are in $0.01, $0.05, $0.10, $0.25, $1, $5, $10, $20 etc.
.40 to make it 8.00, 2.00 to make it 10.00, another 10.00 to make it 20.00 ... needing 4 dimes, 2 dollar bills, and 1 ten bill.
The _idea_ of teaching “what’s actually going on” sounds great.
Problem is, numeracy is not achieved this way; inundating students with greater complexity doesn’t work.
Numeracy is achieved by leading students to an innate grasp of simpler concepts, THEN leading students to discover a higher level which can be achieved with those concepts.
This is little different than the process of learning “estimating” inflicted on me back when. Even then, I understood what they were getting at (having a good innate grasp of numbers), but it seemed staggeringly stupid - clearly even the teachers didn’t have a good grasp of estimating, they were just following a “what’s really going on” notion without really understanding it.