Câu 2. Tính nhẩm:

\(9 \times 5=\) \( 9 \times 6=\) \( 9 \times 7=\) \( 9 \times 8=\)

\(45: 9=\) \( 54: 9=\) \(63: 9=\) \( 72: 9=\)

\(45: 5=\) \( 54: 6=\) \( 63: 7=\) \( 72: 8=\)

Giải

\(9 \times 5=45\) \( 9 \times 6=54\) \( 9 \times 7=63\) \( 9 \times 8=72\)

\(45: 9=5\) \( 54: 9=6\) \(63: 9=7\) \( 72: 9=8\)

\(45: 5=9\) \( 54: 6=9\) \( 63: 7=9\) \( 72: 8=9\)