Đáp án:

 a, 38+41+117+159+6238+41+117+159+62

=(38+62)+(41+159)+117=(38+62)+(41+159)+117

=100     +200      +117=100     +200      +117

=417=417

b, 73+86+968+914+303273+86+968+914+3032

=73+(86+914)+(968+3032)=73+(86+914)+(968+3032)

=73+1000     +4000=73+1000     +4000

=5073=5073

c, 341.67+341.16+659.83341.67+341.16+659.83

=341.(67+16)+659.83=341.(67+16)+659.83

=341.83+659.83=341.83+659.83

=83.(341+659)=83.(341+659)

=83.1000=83000=83.1000=83000

d, 42.53+47.156−47.11442.53+47.156-47.114

=42.53+47.(156−114)=42.53+47.(156-114)

=42.53 +47.42=42.53 +47.42

=42.(53+47)=42.100=42.(53+47)=42.100

=4200=4200

e, 563.23+23.26+23563.23+23.26+23

=23.(563+26+1)=23.(563+26+1)

=23.600=23.600

=13800=13800

f, 132+157+43+68132+157+43+68

=(132+68)+(157+43)=(132+68)+(157+43)

=200      +200=400=200      +200=400

g, 49.68+100.34+6849.68+100.34+68

=49.68+50.68+68=49.68+50.68+68

=68.(49+50+1)=68.(49+50+1)

=68.100=6800=68.100=6800

h, 491.(267+53)+491.(151+67)491.(267+53)+491.(151+67)

=491.(267+53+151+67)=491.(267+53+151+67)

=491.538=491.538

=264158=264158

Vote mk nha.

a)

\(34.86+68.37\)

\(=34.2.43+68.37\)

\(=68\left(43+37\right)=68.70=4760\)

b)

\(47.25+137.49+47.75-37.49\)

\(=47\left(25+75\right)+49\left(137-37\right)\)

\(=47.100+49.100\)

\(=100\left(47+49\right)\)

\(=100.96\)

=9600

34 . 86 + 68 . 37

= 34 . 2 . 43 + 68 . 37

= 68 . 43 + 68 . 37

= 68 . (43 + 37)

= 68 . 100

= 6800

47 . 25 + 137 . 49 + 47 . 75 - 37 . 49

= 47 . (25 + 75) + 49 . (137 - 37)

= 47 . 100 + 49 . 100

= 4700 + 4900

= 9600

a)

\(34.86+68.37\)

\(=34.2.43+68.37\)

\(=68\left(43+37\right)\)

=68.80

=6880

b)

\(47.25+137.49+47.75-37.49\)

=47(25+75) +49(137 - 37 )

=47 . 100+ 49 .100

=100.(47+49)

=100.96

=9600

1. \(x-8+32=68\)

\(x-8=68-32\)

\(x-8=36\)

\(x=36+8\)

\(x=44\)

_____

2. \(x+8+32=68\)

\(x+8=68-32\)

\(x+8=36\)

\(x=36-8\)

\(x=28\)

_____

3. \(98-x+34=43\)

\(98-x=43-34\)

\(98-x=9\)

\(x=98-9\)

\(x=89\)

_____

4. \(98+x-34=43\)

\(98+x=43+34\)

\(98+x=77\)

\(x=77-98\)

\(x=-21\)

_____

5. \(x:5:4=800\)

\(x:5=800.4\)

\(x:5=3200\)

\(x=3200.5\)

\(x=16000\)

_____

6. \(18+x=384:8\)

\(18+x=48\)

\(x=48-18\)

\(x=30\)

_____

7. \(\left(84,6-2\times x\right):3,02=5,1\)

\(84,6-2.x=5,1.3,02\)

\(84,6-2.x=15,402\)

\(2.x=84,6-15,402\)

\(2.x=69,198\)

\(x=69,198:2\)

\(x=34,599\)

_____

8. \(x\times5=120:6\)

\(x.5=20\)

\(x=20:5\)

\(x=4\)

_____

9. \(\left(15\times24-x\right):0,25=100:0,25\)

\(\left(15.24-x\right):0,25=400\)

\(15.24-x=400.0,25\)

\(15.24-x=100\)

\(360-x=100\)

\(x=360-100\)

\(x=260\)

1,x-8+32=68

=>x-8=68-32=36

=>x=36+8=42

2,x+8+32=68

=>x+8=68-32=36

=>x=36-8=28

3,98-x+34=43

=>98-x=43-34=9

=>x=98-9=89

4,98+x-34=43

=>98+x=43+34=77

=>x=77-98=-21

5,x:5:4=800

=>x:20=800

=>x=800x20=16000

6,18+x=384:8=48

=>x=48-18=30

7,(84,6-2x):3,02=5,1

=>84,6-2x=5,1x3,02=15,402

=>2x=84,6-15,402=69,198

=>x=69,198:2=34,599

8,5x=120:6=20

=>x=20:5=4

9,(15x24-x):0,25=100:0,25=400

=>360-x=400x0,25=100

=>x=360-100=260.

1. \(...\Rightarrow x+24=68\Rightarrow x=68-24=44\)

2. \(...\Rightarrow x+40=68\Rightarrow x=68-40=28\)

3. \(...\Rightarrow3^{2\left(8+x\right)}=9=3^2\Rightarrow2\left(8+x\right)=2\Rightarrow8+x=1\Rightarrow x=-7\)

4. \(...\Rightarrow3^{2\left(8+x\right)}=77\) (bạn xem lại đề)

5. \(...\Rightarrow x:5=800.4\Rightarrow x:5=3200\Rightarrow x=3200.5=16000\)

6. \(...\Rightarrow18+x=48\Rightarrow x=48-18=30\)

7. \(...\Rightarrow84,6-2x=5,1.3,02=15,402\Rightarrow2x=84,6-15,402\Rightarrow2x=69,198\Rightarrow x=34,599\)

8. \(...\Rightarrow5.x=20\Rightarrow x=20:5=4\)

9. \(\left(360-x\right):0,25=400\Rightarrow360-x=400.0,25=100\Rightarrow x=400-100=300\)

C. 51; 68 nha bn

\(B\left(17\right)\in\left\{17;34;51;68;85;...\right\}\)

Mà B(17) >50, <70

\(\Rightarrow B\left(17\right)\in\left\{51;68\right\}\)

Chọn C

\(n\times68-24\times n-n\times34=100\)

           \(n\times\left(68-24-34\right)=100\)

                                      \(n\times10=100\)

                                                 \(n=100:10\)

                                                 \(n=10\)

Vậy \(n=10\)

n x 68 - 24 x n - n x 34 = 100
 n x (68-24-34)             = 100
 n x 10                          = 100
 n                                 = 100:10
 n                                 = 10
Vậy n=10

n = 10

tk mình nha! Điểm mình thấp lắm

\(A=\frac{34}{7.13}+\frac{51}{13.22}+\frac{85}{22.37}+\frac{68}{37.49}\)

\(=\frac{17.2}{7.13}+\frac{17.3}{13.22}+\frac{17.5}{22.37}+\frac{17.4}{37.49}\)

\(=17\left(\frac{2}{7.13}+\frac{3}{13.22}+\frac{5}{22.37}+\frac{4}{37.49}\right)\)

\(=\frac{17}{3}\left(\frac{6}{7.13}+\frac{9}{13.22}+\frac{15}{22.37}+\frac{12}{37.49}\right)\)

\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{22}+...+\frac{1}{37}-\frac{1}{49}\right)\)

\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{49}\right)\)\(=\frac{17}{3}.\frac{6}{49}=\frac{17.2}{49}=\frac{34}{49}\)

Có : \(\frac{17}{24}=\frac{34}{48}\)

Vì 48 < 49 => \(\frac{34}{48}>\frac{34}{49}\). Hay \(\frac{17}{24}>A\)

cảm ơn Văn B ? nha !

Bài này viết cũng lâu nữa xin lỗi nha!!!