You may have seen this math problem floating around Facebook recently. It was posted without context, without the teacher’s instruction, and with no other explanation than: “You can’t make this math up…”
Obviously, without any context or instruction, it seems confusing at first, but one math teacher is tired of seeing parents slam the “common core” math system without taking the time to understand why it is being taught that way. Most parents learned the “old” way, “borrowing” from 10 and adding, writing tiny numbers above the equations and trying to keep track of which numbers need to be added. The problem, he says, is that kids don’t understand it as easily.
It is much easier to count up from 12, and this is why.
Say you are a cashier. The line is busy and you’re being hounded by your manager to make change faster. The customer’s total is $3.47, but they hand you a $20 bill. You don’t have time to take out a piece of paper and align the decimal points, decide if you need to carry a ten and figure it out. You grab 3 pennies to reach $3.50, you grab 2 quarters to reach $4.00, you grab a $1 bill to reach $5.00. you grab a $5 bill to reach $10.00, and you grab a $10 bill to reach $20.00. You now have $16.53 in change to give back to the customer and you didn’t have to take out a piece of paper to carry a ten or wait for the till to calculate the total for you.
He thinks parents should be sharing this picture instead:
To a child, this makes a lot more sense than trying to borrow from imaginary numbers to “make ten” and hope you’ve done it right. The real-world application of math is what the common core, or “new math” as one mom put it, is why math is being taught a different way.
What do YOU think schools should be teaching?
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