Delta4Embassy
Gold Member
Subtracting one number from another is now “The Granny Method?” Hunh?
Common Core now wants our kids to learn “Counting-Up Subtraction Method”.
This method of subtracting actually uses addition. For example, like the example given in the book, subtracting 38 from 325 can be derived by counting up. Raise 38 to 40, by going up 2. Raise 40 to 100 by going up 60. Raise 100 to 300 by going up 200. Raise 300 to 325 by going up 25. Then add the jumps together so that 2 + 60 + 200 + 25 = 287. That would be the answer.
Is this system supposed to turn off our kids to math? Or simply befuddle their minds? It certainly makes no sense to me.
Read more: Newer New Math RealClearPolitics
My method, in my head is:
325 - 38 = (100-38)=62+225=200+60+25+2=287
Always reduce figures to 'whole numbers' you're more familar with as with 100, 10, etc. Then break the bigger numbers into smaller component ones so they're easier to work with.
457 x 128 = (457x100)= 45,700+(457x10=4570)x2=9140 +(457x8)= (400x8)+(50x8)+(7x8) = 456+3200=3656 = (45700+9140+3656)=58496
Happens a lot faster in my head than writing it out