math
posted by cristina on .
I need help teaching my 2nd grader how to come up with the answer. Easy for an adult..difficult to explain to a child.
I am thinking of 2 numbers who sum is 15.
One of the numbers is 9 more than the other. Got the 12 plus 3 part. Help me explain it in its simplest terms

I'd use counters  like M & Ms or pennies.

That is my thought but how do I pose the question? I took a deck of cards for counters and tried to figure out how to go about it.

THANK YOU by the way!

Put out 15 objects.
Then have your child take 9 of them away.
How many are left? 
that's not the answer. its how to get her to 12 is 9 more than 3 that equals 15

start with your 15 objects
take 1 away, the pile left is 14 more than what she took away, and 141=13
take 2 away, the pile left is 13 more than what she took away, and 132=11
take 3 away, the pile left is 12 more than what she took away, and 123=9
ahhh, one is 3, the other is 12
for yourself:
x+y = 15
xy = 9
add them
2x = 24
x=12 , then y = 3