Grouping In Tens-by Paul

L-I We are learning to add and subtract tens. 
S-C I am successful when I can solve addition and subtraction with groups of ten.

1. 8 tens + 1 tens = 9 tens
80+10=90
2.6 tens + 2 tens = 8 tens
60 + 20=80
3.  7 tens + 2 tens= 9 tens
70+20=90
4. 5 tens + 4 tens = 9 tens
50 + 40 = 90
5. 9 tens + 1 tens = 100
90+10=100