Part 1:
65 + 25 can be estimated as 70 + 30 = 100.
The exact answer of 65 + 25 = 90.
Part 2:
259 + 43 can be estimated as 260 + 40 = 300.
The exact answer of 259 + 43 = 302
Part 3:
2,009 + 995 = can be estimated as 2,000 + 1,000 = 3,000.
The exact answer of 2,009 + 995 = 3,004.
