toán 5 bài 4 trang 43

\(a) \dfrac{{36 \times 45}}{{6 \times 5}} = \dfrac{{6 \times 6 \times 5 \times 9}}{{6 \times 5}} = 54\)

\(b) \dfrac{{56 \times 63}}{{9 \times 8}} = \dfrac{{7 \times 8 \times 7 \times 9}}{{9 \times 8}} = 49.\)