Discuss with students what is
common in all these questions. See
if students can develop a
generalization about subtraction
when the digits in the ones places
are the same.
30
20
25
3
Possible strategy: I know that
13 is a teen and 10 + 3 = 13.
So, 13 − 3 = 10.
Ongoing Assessment
Use DPP item T to assess students'
abilities to use mental math
strategies to solve subtraction
problems with larger numbers [E4].
