Bài tập 68 trang 35 SGK Toán 6 Tập 2

a, \(\dfrac{1}{3}.\dfrac{4}{5}+\dfrac{1}{3}.\dfrac{6}{5}-\dfrac{4}{3}\)

b, \(\dfrac{4}{19}-\dfrac{-3}{7}+\dfrac{-3}{7}.\dfrac{15}{19}+\dfrac{5}{7}\)

c, \(\dfrac{5}{9}.\dfrac{7}{13}+\dfrac{5}{9}.\dfrac{9}{13}-\dfrac{5}{9}.\dfrac{3}{13}\)

nhom tho gat thu nhat nhat duoc 3/8 dien tich thua ruong,nho thi gat thu hai gat duoc 3/5 dien tich thua ruong .Nhom thu hai gat nhieu hon nhom thu nhat 108 m vuong. Tinh dien tich thua ruong moi nhom gat duoc

Tính 

M = \(\dfrac{1}{2}\) + \(\dfrac{1}{2.3}\) + \(\dfrac{1}{3.4}\) +....+ \(\dfrac{1}{49.50}\)