1. Tính nhẩm:a)\(\begin{array}{l}2 \times 6 =.....\\3 \times 6 =.....\\4 \times 6 =.....\\5 \times 6 =.....\end{array}\) \(\begin{array}{l}5 \times 10 =.....\\4 \times 9 =.....\\3 \times 8 =.....\\2 \times 7 =.....\end{array}\) \(\begin{array}{l}5 \times 5 =.....\\4 \times 4 =.....\\3...