Odpowiedź :
Odpowiedź:
a) ( 1 - 5/7) *0,49= ( 7/7-5/7)*0,49= 2/7 *49/100( skracamy 7 i 49 przez 7, oraz
2 i 100 przez 2)= 7/50= 14/100= 0,14
b) 1 i 3/8 - ( 0,9 -3/4)= 1 i 3/8 - ( 0,9 - 0,75)= 1 i 3/8 - 0,15= 1 i 3/8- 15/100=
= 1 i 3/8- 3/20 = 1 i 15/40- 6/40= 1 i 9/40
c) 3 + [ 1- ( 7/5 -0,9)]= 3 + [1 -( 14/10 -9/10)]= 3+ [ 1- 5/10)= 3+ ( 5/10)= 3,5
d) 2,4 *1/3 + 4,8 : 2 i 2/5= 24/10 *1/3 + 48/10 : 12/5 ( skracamy 24 i 3 przez
3)= 8/10 + 48/10 *5/12( skracamy 48 i 12 przez 12 ,oraz 5 i 10 przez
5)= 8/10 + 2= 2 i 8/10= 2,8
e) (1/2 + 0,4) *( 3/4 -0,2)= ( 5/10 + 4/10) * 3/4- 2/10)= 9/10 *( 15/20- 4/20)=
= 9/10 * 11/20 = 99/200= 495/1000= 0,495
f) 4 - ( 2,5 -1 i 1/5 ) *9/13= 4- ( 2 i 5/10- 1 i 2/10)*9/13= 4- ( 1 i 3/10)*9/13=
= 4- 13/10*9/13 ( skracamy9 i 9 przez 9, oraz 13 i 13 przez 13)=
= 4- 9/10= 3 i 10/10- 9/10= 3 i 1/10= 3,1=3
Szczegółowe wyjaśnienie:
[tex]a) \ (1-\frac{5}{7})\cdot0,49 =(\frac{7}{7}-\frac{5}{7})\cdot\frac{49}{100} = \frac{2}{7}\cdot\frac{49}{100} = \frac{7}{50} =0,14[/tex]
[tex]b) \ 1\frac{3}{8}-(0,9-\frac{3}{4}) =1\frac{3}{8}-(\frac{9}{10}-\frac{3}{4}) = 1\frac{3}{8}-(\frac{18}{20}-\frac{15}{20}) = 1\frac{3}{8}-\frac{3}{20}=1\frac{14}{40}-\frac{6}{40} = \\\\=1\frac{9}{40}=1,225[/tex]
[tex]c) \ 3+[1-(\frac{7}{5}-0,9)] = 3+[1-(\frac{14}{10}-\frac{9}{10})] = 3+[1-\frac{5}{10}] = 3+\frac{5}{10} = 3+\frac{1}{2} = 3\frac{1}{2}=3,5[/tex]
[tex]d) \ 2,4\cdot\frac{1}{3} + 4,8:2\frac{2}{5} = \frac{24}{10}\cdot\frac{1}{3}+\frac{48}{10}:\frac{12}{5} =\frac{8}{10}+\frac{24}{5}\cdot\frac{5}{12} =\frac{8}{10}+2 = 2\frac{8}{10} = 2,8[/tex]
[tex]e) \ (\frac{1}{2}+0,4)\cdot(\frac{3}{4}-0,2)=(\frac{1}{2}+\frac{4}{10})\cdot(\frac{3}{4}-\frac{2}{10}) = (\frac{1}{2}+\frac{2}{5})\cdot(\frac{3}{4}-\frac{1}{5}) = (\frac{5}{10}+\frac{4}{10})\cdot(\frac{15}{20}-\frac{4}{20}) =\\\\=\frac{9}{10}\cdot\frac{11}{20}=\frac{99}{200}=0,495[/tex]
[tex]f) \ 4-(2,5-1\frac{1}{5})\cdot\frac{9}{13} = 4-(\frac{25}{10}-\frac{6}{5})\cdot\frac{9}{13} = 4-(\frac{25}{10}-\frac{12}{10})\cdot\frac{9}{13} = 4-\frac{13}{10}\cdot\frac{9}{13} =\\\\=4-\frac{9}{10} = 3\frac{10}{10}-\frac{9}{10} = 3\frac{1}{10} = 3,1[/tex]