Answer:
The numbers which have unit digit Zero for a two digit number, and for three digit number ones and tens place should be equipped with zero,So on..... does not require addends to group together.
For example, addition problem in which you would not regroup addends
→ 10+20+30
→ 30 +40 +50
→ 100+200+300
And Addition Problems in which you will regroup addends
→ 17 +5 +3=(17+3)+5=20+5=25
→ 4+9+6=(4+6)+9=10+9=19
→ 13+19+17=(13+17)+19=30+19=49