19.100克盐放入400克水中,含盐率是( )
| A. | 25% | B. | 20% | C. | 40% |
18.一个半圆形教具,它的半径为5分米,它的周长是( )
0 140566 140574 140580 140584 140590 140592 140596 140602 140604 140610 140616 140620 140622 140626 140632 140634 140640 140644 140646 140650 140652 140656 140658 140660 140661 140662 140664 140665 140666 140668 140670 140674 140676 140680 140682 140686 140692 140694 140700 140704 140706 140710 140716 140722 140724 140730 140734 140736 140742 140746 140752 140760 199269
| A. | 15.7分米 | B. | 78.5分米 | C. | 25.7分米 |