Question

Đã trả lời bởi chuyên gia

Answer 1

`a) 7/20 - (5/8 - 2/5)`

`= 7/20 - (25/40 - 16/40)`

`= 7/20 - 9/40`

`= 14/40 - 9/40`

`= 5/40 = 1/8`

`b) 5/6 + (5/9 - 1/4)`

`= 5/6 + ( 20/36 - 9/36)`

`= 30/36 + 11/36`

`= 41/36`

`c) 9/10 - (2/5 + 3/10) + 7/20`

`= 18/20 - (8/20 + 6/20) + 7/20`

`= 18/20 - 14/20 + 7/20`

`= 11/20`

Answer 2

a,

$\frac{7}{20} - (\frac{5}{8} - \frac{2}{5}) = \frac{7}{20} - \frac{5}{8} + \frac{2}{5} = \frac{7 \times 2}{20 \times 2} - \frac{5 \times 5}{8 \times 5} + \frac{2 \times 8}{5 \times 8} = \frac{14}{40} - \frac{25}{40} + \frac{16}{40} = \frac{5}{40} = \frac{1}{8} b, \frac{5}{6} + (\frac{5}{9} - \frac{1}{4}) = \frac{5}{6} + \frac{5}{9} - \frac{1}{4} = \frac{5 \times 6}{6 \times 6} + \frac{5 \times 4}{9 \times 4} - \frac{1 \times 9}{4 \times 9} = \frac{30}{36} + \frac{20}{36} - \frac{9}{36} = \frac{41}{36} c, \frac{9}{10} - (\frac{2}{5} + \frac{3}{10}) + \frac{7}{20} = \frac{9}{10} - \frac{2}{5} - \frac{3}{10} + \frac{7}{20} = \frac{9 \times 2}{10 \times 2} - \frac{2 \times 4}{5 \times 4} - \frac{3 \times 2}{10 \times 2} + \frac{7}{20} = \frac{18}{20} - \frac{8}{20} - \frac{6}{20} + \frac{7}{20} = \frac{18 - 8 - 6 + 7}{20} = \frac{11}{20}$

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Answer 3

a,

$\frac{7}{20} - (\frac{5}{8} - \frac{2}{5}) = \frac{7}{20} - \frac{5}{8} + \frac{2}{5} = \frac{7 \times 2}{20 \times 2} - \frac{5 \times 5}{8 \times 5} + \frac{2 \times 8}{5 \times 8} = \frac{14}{40} - \frac{25}{40} + \frac{16}{40} = \frac{5}{40} = \frac{1}{8} b, \frac{5}{6} + (\frac{5}{9} - \frac{1}{4}) = \frac{5}{6} + \frac{5}{9} - \frac{1}{4} = \frac{5 \times 6}{6 \times 6} + \frac{5 \times 4}{9 \times 4} - \frac{1 \times 9}{4 \times 9} = \frac{30}{36} + \frac{20}{36} - \frac{9}{36} = \frac{41}{36} c, \frac{9}{10} - (\frac{2}{5} + \frac{3}{10}) + \frac{7}{20} = \frac{9}{10} - \frac{2}{5} - \frac{3}{10} + \frac{7}{20} = \frac{9 \times 2}{10 \times 2} - \frac{2 \times 4}{5 \times 4} - \frac{3 \times 2}{10 \times 2} + \frac{7}{20} = \frac{18}{20} - \frac{8}{20} - \frac{6}{20} + \frac{7}{20} = \frac{18 - 8 - 6 + 7}{20} = \frac{11}{20}$

Answer 4

A)7/20-(5/8-2/5)=
7/20-9/40=1/8
B)5/6+(5/9-1/4)=
5/6+11/36=41/36
C)9/10-(2/5+3/10)+7/20 =9/10-7/10+7/10=9/10

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