15．估算．
| 55÷8≈ | 199÷2≈ | 31÷6≈ |
| 71×39≈ | 43×21≈ | 22×89≈ |
14．口算．
| 400÷4= | 10×40= | 11×20= |
| 0÷5= | 90×20= | 200×7= |
| 4800÷6= | 72×10= | 300÷5= |
13．8月份有（ ）天．
0 159539 159547 159553 159557 159563 159565 159569 159575 159577 159583 159589 159593 159595 159599 159605 159607 159613 159617 159619 159623 159625 159629 159631 159633 159634 159635 159637 159638 159639 159641 159643 159647 159649 159653 159655 159659 159665 159667 159673 159677 159679 159683 159689 159695 159697 159703 159707 159709 159715 159719 159725 159733 199269
| A． | 28 | B． | 30 | C． | 31 |
