Giải câu 1 bài : Luyện tập chung sgk Toán 5 trang 176

a) 

 683 x 35 = 23905

1954 x 425 = 830450

2438 x 306 = 746028

b\(\frac{7}{9}\) x \(\frac{3}{35}\) = \(\frac{7 \times 3}{9 \times 35}\)   = \(\frac{7 \times 3}{3 \times 3 \times 5 \times 7}\)    = \(\frac{1}{3 \times 5}\)  = \(\frac{1}{15}\)

\(\frac{9}{22}\)  x 55 = \(\frac{9 \times 55}{22}\)   = \(\frac{9 \times 5 \times 11}{2 \times 11}\)   = \(\frac{9 \times 5}{2}\)   = \(\frac{45}{2}\)  

\(\frac{11}{17}\) :  \(\frac{33}{34}\) = \(\frac{11}{17}\) x \(\frac{34}{33}\) = \(\frac{11 \times 34}{17 \times 33}\) = \(\frac{11 \times 2 \times 17}{17 \times 3 \times 11}\)  = \(\frac{2}{3}\) 

d)