How do I teach this math concept?

[Slipper]

We have struggled with this concept for quite some time.

 

This is for dd7 (will be 8 in December and is in 2nd grade).

 

What is 3+2? (answer 5, no problem)

What is 13+2? (long pause, answer 15)

What is 23+2? (long pause and I point out that the 3+2 hasn't changed, only the 10's value has one more added to it than the previous answer. Longer pause, answer 20. No. Answer 18. I remind that we're adding. Long pause again so I show her how 3+2 is the same, only the first number has changed. She gets the right answer.)

 

Then we move on to 7+1 (answer 8, no problem)

What is 17+1 (long pause, answer 18)

What is 27+1 (garbled repeat of the above.)

 

I moved back to place value thinking that it would help. Some days it's clear, occasionally she gets confused again. For the past four days, she's been okay with place value perfectly which is why I tried these problems again.

 

What am I doing wrong?

[regentrude]

Have you tried using manipulatives? Cuisenaire rods, if you have, gummy bears or m&m's if you don't?

I'd use one color to set out the complete tens (10, 20) and a different color for the ones.

[Spy Car]

We have struggled with this concept for quite some time.

 

This is for dd7 (will be 8 in December and is in 2nd grade).

 

What is 3+2? (answer 5, no problem)

What is 13+2? (long pause, answer 15)

What is 23+2? (long pause and I point out that the 3+2 hasn't changed, only the 10's value has one more added to it than the previous answer. Longer pause, answer 20. No. Answer 18. I remind that we're adding. Long pause again so I show her how 3+2 is the same, only the first number has changed. She gets the right answer.)

 

Then we move on to 7+1 (answer 8, no problem)

What is 17+1 (long pause, answer 18)

What is 27+1 (garbled repeat of the above.)

 

I moved back to place value thinking that it would help. Some days it's clear, occasionally she gets confused again. For the past four days, she's been okay with place value perfectly which is why I tried these problems again.

 

What am I doing wrong?

 

Try asking how many Units (or Ones if you prefer that name for the "place") do we have when solving a problem like 23+2?

 

5-Units.

 

How many Tens do we have?

 

2-Tens.

 

What do we call 2-Tens 5-Units/Ones?

 

Twenty-five.

 

Repeat endlessly.

 

Bill

[Slipper]

I have the complete set of mathusee manipulatives (two boxes actually). We went through 1's and 10's up to 100.

 

If I ask her what do we get when I have 5 tens and 3 ones, she knows the answer is 53. Spycar, I'll try to break it down further as you suggested.

[Arcadia]

Then we move on to 7+1 (answer 8, no problem)

What is 17+1 (long pause, answer 18)

What is 27+1 (garbled repeat of the above.)

 

My younger one did those by expanding the double digit number in his head.

 

17+1 = 10+7+1 = 10 + 8

27+1 = 20+7+1 = 20+8

[Spy Car]

I have the complete set of mathusee manipulatives (two boxes actually). We went through 1's and 10's up to 100.

 

If I ask her what do we get when I have 5 tens and 3 ones, she knows the answer is 53. Spycar, I'll try to break it down further as you suggested.

 

It is seemingly such a small thing to us (as adults) but it can make a huge difference to children to keep talking about numbers in terms that include their place value. People often refer to these as "math names."

 

I like each place to get a name in a math name scheme, so 3-Hundreds 6-Tens 5-Units (Ones) for 365. It might seem like overdoing it to approach addition and subtraction problems by talking through how many Hundrends, Tens, and Units you are dealing with each (and every) time. But it pays off.

 

Demonstrating or modeling the problems with C Rods and base-10 flats can be very useful for younger children along with the discussion about the values in each place. The MUS blocks would serve the same function.

 

Bill

 

ETA: I'm not a fan of the MUS math name scheme: 1-T 2 (onety two) for twelve. 1-Ten 2-Units is more helpful IMO.

Edited October 12, 2012 by Spy Car

[Slipper]

It is seemingly such a small thing to us (as adults) but it can make a huge difference to children to keep talking about numbers in terms that include their place value. People often refer to these as "math names."

 

I like each place to get a name in a math name scheme, so 3-Hundreds 6-Tens 5-Units (Ones) for 365. It might seem like overdoing it to approach addition and subtraction problems by talking through how many Hundrends, Tens, and Units you are dealing with each (and every) time. But it pays off.

 

Demonstrating or modeling the problems with C Rods and base-10 flats can be very useful for younger children along with the discussion about the values in each place. The MUS blocks would serve the same function.

 

Bill

 

ETA: I'm not a fan of the MUS math name scheme: 1-T 2 (onety two) for twelve. 1-Ten 2-Units is more helpful IMO.

 

Bill,

I don't do their name scheme. The onety two was too much for me.

My middle daughter catches on quickly and I'm afraid I'm guilty of expecting my youngest to do the same. Patience is the key I guess. :)

[spaceman]

You could also match labels to the blocks. You can use index cards. Write (or have her write) the tens. 60 - or 6 tens.

 

Then cut some index cards in half. Have her write the units on that card. 2 units. Then put the unit card on top of the unit part of her tens (the 0 in 60, "there are 0 units in 60").

 

 

 

You can also use markers to match the unit and ten colors of your blocks. Have her use those colors as she does her work. It'll make her stop and think which group she is adding.

[Shelsi]

Bill,

I don't do their name scheme. The onety two was too much for me.

My middle daughter catches on quickly and I'm afraid I'm guilty of expecting my youngest to do the same. Patience is the key I guess. :)

 

I wasn't a fan either and never did the onety-two type stuff with my ds. However he's very mathy and picked up on stuff super quick. My kindy dd is having a much harder time and I finally went to using "onety-one" and "fivety-three" type naming and the light bulb totally went on for her. So while it's irritating I have to admit it definitely helps some kids.

[Spy Car]

Bill,

I don't do their name scheme. The onety two was too much for me.

My middle daughter catches on quickly and I'm afraid I'm guilty of expecting my youngest to do the same. Patience is the key I guess. :)

 

Try a mix of blocks and talking through the problems using the name schemes in a sustained way and I bet it does the trick. She obviously can add the sums, but it is often the semantics that confuse children of this age.

 

Reenforcing place value is the way to go. And you can (should) add the English names too. But even in the future, a raised eyebrow and a question of, "how many Tens?" or how many Units?" will set them straight when their calculations are off. It does take patience. That is true. It is worth the effort.

 

Bill