Question

[Nguyễn Thị Hạnh Dung]

Tính bằng cách thuận tiện nhất:

. 49/5 - 1/2 - 1/4 - 1/8 - 1/16 - 1/32

 21/11 - 9/19 - 3/19 - 12/38 + 24/22

. 2/3 + 3/4 + 4/5 + 12/9 + 28/16 + 48/15

 39/16 : 5/8 - 7/16 : 5/8 + 4/5

 16/17 x 12/19 + 16/17 x 7/19 - 2/3

Answer 1

[Nguyễn Lê Phước Thịnh]

a: \(\dfrac{49}{5}-\dfrac{1}{2}-\dfrac{1}{4}-\dfrac{1}{8}-\dfrac{1}{16}-\dfrac{1}{32}\)

\(=\dfrac{49}{5}-\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}\right)\)

\(=\dfrac{49}{5}-\dfrac{16+8+4+2+1}{32}\)

\(=\dfrac{49}{5}-\dfrac{31}{32}=\dfrac{1413}{160}\)

b: \(\dfrac{21}{11}-\dfrac{9}{19}-\dfrac{3}{19}-\dfrac{12}{38}+\dfrac{24}{22}\)

\(=\left(\dfrac{21}{11}+\dfrac{12}{11}\right)-\left(\dfrac{9}{19}+\dfrac{3}{19}+\dfrac{6}{19}\right)\)

\(=3-\dfrac{18}{19}=\dfrac{3\cdot19-18}{19}=\dfrac{57-18}{19}=\dfrac{39}{19}\)

c: \(\dfrac{2}{3}+\dfrac{3}{4}+\dfrac{4}{5}+\dfrac{12}{9}+\dfrac{28}{16}+\dfrac{48}{15}\)

\(=\left(\dfrac{2}{3}+\dfrac{4}{5}+\dfrac{48}{15}\right)+\left(\dfrac{3}{4}+\dfrac{4}{3}+\dfrac{7}{4}\right)\)

\(=\left(\dfrac{10}{15}+\dfrac{12}{15}+\dfrac{48}{15}\right)+\left(\dfrac{5}{2}+\dfrac{4}{3}\right)\)

\(=\dfrac{70}{45}+\dfrac{23}{6}\)

\(=\dfrac{23}{6}+\dfrac{14}{9}=\dfrac{97}{18}\)

d: \(\dfrac{39}{16}:\dfrac{5}{8}-\dfrac{7}{16}:\dfrac{5}{8}+\dfrac{4}{5}\)

\(=\left(\dfrac{39}{16}-\dfrac{7}{16}\right):\dfrac{5}{8}+\dfrac{4}{5}\)

\(=2\cdot\dfrac{8}{5}+\dfrac{4}{5}=\dfrac{16}{5}+\dfrac{4}{5}=\dfrac{20}{5}=4\)

e: \(\dfrac{16}{17}\times\dfrac{12}{19}+\dfrac{16}{17}\times\dfrac{7}{19}-\dfrac{2}{3}\)

\(=\dfrac{16}{17}\times\left(\dfrac{12}{19}+\dfrac{7}{19}\right)-\dfrac{2}{3}\)

\(=\dfrac{16}{17}-\dfrac{2}{3}=\dfrac{48-34}{51}=\dfrac{14}{51}\)

Answer 2

[Nguyễn Thị Hạnh Dung]

giúp tui với ;(( khó qué