Question

[Khánh Linh]

BT3: Tính nhanh:

1) \(\dfrac{5}{18}+\dfrac{4}{7}+\dfrac{13}{18}+\dfrac{3}{7}\)

2) \(\dfrac{4}{9}.\dfrac{5}{19}.\dfrac{9}{4}\)

Answer 1

[Nguyên]

1.

a) \(\dfrac{5}{18}+\dfrac{4}{7}+\dfrac{13}{18}+\dfrac{3}{7}\)

\(=\left(\dfrac{5}{18}+\dfrac{13}{18}\right)+\left(\dfrac{4}{7}+\dfrac{3}{7}\right)\)

\(=1+1=2\)

b) \(\dfrac{4}{9}.\dfrac{5}{19}.\dfrac{9}{4}\)

\(=\left(\dfrac{4}{9}.\dfrac{9}{4}\right).\dfrac{5}{19}\)

\(=1.\dfrac{5}{19}=\dfrac{5}{19}\)

tik mik nha!!!

Answer 2

[Nguyễn Thị Anh Thư]

2) \(\dfrac{4}{9}.\dfrac{5}{19}.\dfrac{9}{4} =(\dfrac{4}{9}.\dfrac{9}{4}).\dfrac{5}{19} =1.\dfrac{5}{19} =\dfrac{5}{19}\)