Câu 1. Tính nhẩm

\(18: 9=\) \(27: 9=\) \(54: 9=\) \(63: 9=\)

\(45: 9=\) \(72: 9=\) \(36: 9=\) \(63: 9=\)

\(9: 9=\) \(90: 9=\) \( 81: 9=\) \(72: 8=\)

Giải:

\(18: 9=2\) \(27: 9=3\) \(54: 9=6\) \(63: 9=7\)

\(45: 9=5\) \(72: 9=8 \) \( 36: 9=4\) \( 63: 7=9\)

\(9: 9=1\) \(90: 9=10\) \(81: 9=9\) \(72: 8=9\)