Question

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Answer 1

a, = $2, 75 . (- 0, 4) - 1, 6 . 2, 75 + (- 1, 2) . \frac{11}{4}$

= 2,75 . (-0,4)-1,6 . 2,75 + (-1,2) . 2,75

= 2,75 . ( (-0,4)-1,6+ (-1,2) )

=2,75 . (-3,2)

=-8,8

b, = (7/3+7/2) : ( -25/6+22/7)+15/2

= 35/6: (-43/42)+15/2

= 35/6 $\times$ (-42/43)+15/2

=-245/43 +15/2

=155/86

c, = $\frac{5}{7} . (\frac{5}{11} + \frac{2}{11} - \frac{14}{11}) = \frac{5}{7} . (\frac{- 7}{11}) = - 5 / 11$

d, = 1/5.1/3+1/5.1/7+1/7.1/9+1/9.1/11+1/11.1/13+1/15.1/13

= $\frac{1}{5} . (1 / 3 + 1 / 7) + \frac{1}{9} . (\frac{1}{7} + \frac{1}{11}) + 1 / 13 . (1 / 11 + \frac{1}{15})$

= 1/5.10/21+1/9.18/77+1/13.26/165

= $\frac{2}{21} + 2 / 77 + \frac{2}{165}$

= 2/15

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Answer 2

a, = $2, 75 . (- 0, 4) - 1, 6 . 2, 75 + (- 1, 2) . \frac{11}{4}$

= 2,75 . (-0,4)-1,6 . 2,75 + (-1,2) . 2,75

= 2,75 . ( (-0,4)-1,6+ (-1,2) )

=2,75 . (-3,2)

=-8,8

b, = (7/3+7/2) : ( -25/6+22/7)+15/2

= 35/6: (-43/42)+15/2

= 35/6 $\times$ (-42/43)+15/2

=-245/43 +15/2

=155/86

c, = $\frac{5}{7} . (\frac{5}{11} + \frac{2}{11} - \frac{14}{11}) = \frac{5}{7} . (\frac{- 7}{11}) = - 5 / 11$

d, = 1/5.1/3+1/5.1/7+1/7.1/9+1/9.1/11+1/11.1/13+1/15.1/13

= $\frac{1}{5} . (1 / 3 + 1 / 7) + \frac{1}{9} . (\frac{1}{7} + \frac{1}{11}) + 1 / 13 . (1 / 11 + \frac{1}{15})$

= 1/5.10/21+1/9.18/77+1/13.26/165

= $\frac{2}{21} + 2 / 77 + \frac{2}{165}$

= 2/15

Answer 3

a) $2 \frac{3}{4} . (- 0, 4) - 1 \frac{3}{5} . 2, 75 + (- 1, 2) : \frac{4}{11} = \frac{11}{4} . (- 0, 4) - \frac{8}{5} . \frac{11}{4} + (- 1, 2) . \frac{11}{4} = \frac{11}{4} . (- 0, 4 - 1, 6 - 1, 2) = \frac{11}{4} . \frac{- 16}{5} = - \frac{44}{5}$

b) $(2 \frac{1}{3} + 3 \frac{1}{2}) : (- 4 \frac{1}{6} + 3 \frac{1}{7}) + 7 \frac{1}{2} = (\frac{7}{3} + \frac{7}{2}) : (\frac{- 25}{6} + \frac{22}{7}) + \frac{15}{2} = (\frac{14 + 21}{6}) : (\frac{- 175 + 132}{42}) + \frac{15}{2} = \frac{35}{6} : \frac{- 43}{42} + \frac{15}{2} = \frac{- 245}{43} + \frac{15}{2} = \frac{- 245.2 + 15.43}{86} = \frac{155}{86}$

c) $\frac{5}{7} . \frac{5}{11} + \frac{5}{7} . \frac{2}{11} - \frac{5}{7} . \frac{14}{11} = \frac{5}{7} . (\frac{5}{11} + \frac{2}{11} - \frac{14}{11}) = \frac{5}{7} . \frac{- 7}{11} = - \frac{5}{11}$

d) $2 A = 2 . (\frac{1}{15} + \frac{1}{35} + \frac{1}{63} + \frac{1}{99} + \frac{1}{143} + \frac{1}{195}) = 2 . (\frac{1}{3} . \frac{1}{5} + \frac{1}{5} . \frac{1}{7} + \frac{1}{7} . \frac{1}{9} + \frac{1}{9} . \frac{1}{11} + \frac{1}{11} . \frac{1}{13} + \frac{1}{13} . \frac{1}{15}) = \frac{5 - 3}{3.5} + \frac{7 - 5}{5.7} + \frac{9 - 7}{7.9} + \frac{11 - 9}{9.11} + \frac{13 - 11}{11.13} + \frac{15 - 13}{13.15} = \frac{5}{3.5} - \frac{3}{3.5} + . . . . . + \frac{15}{13.15} - \frac{13}{13.15} = \frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7} + . . . . - \frac{1}{15} = \frac{1}{3} - \frac{1}{15} = \frac{4}{15} = > A = \frac{2}{15} =$

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Answer 4

a) $2 \frac{3}{4} . (- 0, 4) - 1 \frac{3}{5} . 2, 75 + (- 1, 2) : \frac{4}{11} = \frac{11}{4} . (- 0, 4) - \frac{8}{5} . \frac{11}{4} + (- 1, 2) . \frac{11}{4} = \frac{11}{4} . (- 0, 4 - 1, 6 - 1, 2) = \frac{11}{4} . \frac{- 16}{5} = - \frac{44}{5}$

b) $(2 \frac{1}{3} + 3 \frac{1}{2}) : (- 4 \frac{1}{6} + 3 \frac{1}{7}) + 7 \frac{1}{2} = (\frac{7}{3} + \frac{7}{2}) : (\frac{- 25}{6} + \frac{22}{7}) + \frac{15}{2} = (\frac{14 + 21}{6}) : (\frac{- 175 + 132}{42}) + \frac{15}{2} = \frac{35}{6} : \frac{- 43}{42} + \frac{15}{2} = \frac{- 245}{43} + \frac{15}{2} = \frac{- 245.2 + 15.43}{86} = \frac{155}{86}$

c) $\frac{5}{7} . \frac{5}{11} + \frac{5}{7} . \frac{2}{11} - \frac{5}{7} . \frac{14}{11} = \frac{5}{7} . (\frac{5}{11} + \frac{2}{11} - \frac{14}{11}) = \frac{5}{7} . \frac{- 7}{11} = - \frac{5}{11}$

d) $2 A = 2 . (\frac{1}{15} + \frac{1}{35} + \frac{1}{63} + \frac{1}{99} + \frac{1}{143} + \frac{1}{195}) = 2 . (\frac{1}{3} . \frac{1}{5} + \frac{1}{5} . \frac{1}{7} + \frac{1}{7} . \frac{1}{9} + \frac{1}{9} . \frac{1}{11} + \frac{1}{11} . \frac{1}{13} + \frac{1}{13} . \frac{1}{15}) = \frac{5 - 3}{3.5} + \frac{7 - 5}{5.7} + \frac{9 - 7}{7.9} + \frac{11 - 9}{9.11} + \frac{13 - 11}{11.13} + \frac{15 - 13}{13.15} = \frac{5}{3.5} - \frac{3}{3.5} + . . . . . + \frac{15}{13.15} - \frac{13}{13.15} = \frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7} + . . . . - \frac{1}{15} = \frac{1}{3} - \frac{1}{15} = \frac{4}{15} = > A = \frac{2}{15} =$

Số thứ tự	Loại hàng	Số lượng (quyển)	Giá đơn vị (đồng)	Tổng số tiền (đồng)
1	Vở loại 1	35	2000	...
2	Vở loại 2	42	1500	...
3	Vở loại 3	38	1200	...
Cộng:				...

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