I think what helped my son with this was to think of it as 6-ten+6-ten=12-ten. He then convert 12-ten to 12 tens which is 120. After awhile, it got easier and easier and he could skip the 6-ten step and think of it as 60+60.

We used side B of the abacus alot. Also, playing the games Corners helped alot. I found sometimes things just need to simmer while. I'd move on to some geometry or coin exercises while still giving 2digit problems.

hth

Jana, did stating 6 ten + 6 ten help with solving 60 + 60? That is exactly what I would have recommended. Good job captuhuta! I would also add having your child touch the numbers when saying them as well. So sliding over the 12 and saying twelve, then lifting the finger and tapping on the 0 and saying ten.

If you happen to have two abacuses you can also show this by using the front sides. Place the abacuses one under the other. On the abacus on top show 60 beads. Then add 60 more beads which of course makes you go over 100. Do this slowly asking your child to try this first. If there seems to be some confusion, what your child through it while having your child move 6 ten and then another 6 ten.

See if this helps and let us know how it goes.

Sincerely, Rosine