a) -( -35 + 7 - 13 ) + ( 2 - 35 ) - ( 13 - 7 )

= 35 - 7 + 13 + 2 - 35 - 13 + 7

= ( 35 - 35 ) + ( -7 + 7 ) + ( 13 - 13 ) + 2

= 0 + 0 + 0 + 2

= 2

b) ( 70 + 8 - 35 ) - ( 8 - 37 - 10 ) - 70 

= 70 + 8 - 35 - 8 + 37 + 10 - 70

= ( 70 - 70 ) + ( 8 - 8 ) + ( -35 + 37 ) + 10

= 0 + 0 + 2 + 10

= 12 

c) 5 - ( 14 + 4 - 52 ) - ( 52 - 14 ) + 4

= 5 - 14 - 4 + 52 - 52 + 14 + 4

= 5 - ( 14 + 14 ) + ( 52 - 52 ) + ( -14 + 14 )

= 5 - 14 - 14 + 0 + 0

= 5 - ( 14 - 14 )

= 5 - 0

= 5

kinh day ban oi

1: =20*(-4)+24(-30)

=-80-720=-800

2: =-13*57+13*32+57*13-57*45

=13*32-57*45=-2149

3: =-12*8*125

=-12*1000=-12000

4: =(-134)(1-51+48)

=(-134)*(-2)=268

5: =(-24)(45-5)=40*(-24)=-960

a,43.27 + 93.43+ 57.61 + 59.57

=43.(27+93)+57.(61+59)

=43.120+57.120

=(43+57).120

=100.120

=12000

b,16.41 + 37.34 + 11.41 + 25.37

=41.(16+11)+37.(34+25)

=41.27+37.59

=1107+2183

=3290

c,23.39 + 58.35 + 25.39 +26.58

=(23+25).39+58.(35+26)

=48.39+58.61

=1872+3538

=5410

d,36.6 + 6.37 + 31.73 + 73.23

=(37+36).6 + (31+23).73

=73.6 + 54.73

=73.(6+54)

=73.60

=133

**** nhes

e,64.6 + 81.4 + 17.6

a,43.27 + 93.43+ 57.61 + 59.57

=43.(27+93)+57.(61+59)

=43.120+57.120

=(43+57).120

=100.120

=12000

b,16.41 + 37.34 + 11.41 + 25.37

=41.(16+11)+37.(34+25)

=41.27+37.59

=1107+2183

=3290

c,23.39 + 58.35 + 25.39 +26.58

=(23+25).39+58.(35+26)

=48.39+58.61

=1872+3538

=5410

d,36.6 + 6.37 + 31.73 + 73.23

=(37+36).6 + (31+23).73

=73.6 + 54.73

=73.(6+54)

=73.60

=133

Tính còn sai phải là 120000

nó sẽ bằng

=24x15-24x4+24x4-24x15

=(24x15-24x15)+(24x4-24x4)

=0

Ta có:\(24.\left(15-4\right)+4.\left(24-15\right)\)

\(=24.15-24.4+4.24-15.4\)\(=24.15-15.4\)

\(=15.\left(24-4\right)\)

\(=15.20=300\)

\(24\left(15-4\right)+4\left(24-15\right)\)

\(=24.15-24.4+4.24-4.15\)

\(=\left(24.15-4.15\right)+\left(4.24-24.4\right)\)

\(=15\left(24-4\right)+0\)

\(=15.20\)

\(=300\)

áp dụng kiến thức tính nhanh ý

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=1275

= 1275

=1275

=1245

Có ai rảnh đâu mà đi ngồi cộng ngần đấy số ra.

300

300

= 300 

\(\dfrac{19}{28}+\dfrac{23}{47}-\dfrac{15}{8}+\dfrac{9}{28}+\dfrac{24}{47}\)

\(=\left(\dfrac{19}{28}+\dfrac{9}{28}\right)+\left(\dfrac{23}{47}+\dfrac{24}{47}\right)-\dfrac{15}{8}\)

\(=\dfrac{28}{28}+\dfrac{47}{47}-\dfrac{15}{8}\)

\(=1+1-\dfrac{15}{8}\)

\(=\dfrac{1}{8}\)

____________________

\(\dfrac{30}{11}+\dfrac{12}{35}-\dfrac{19}{11}-\dfrac{2}{35}-\dfrac{2}{7}\)

\(=\left(\dfrac{30}{11}-\dfrac{19}{11}\right)+\left(\dfrac{12}{35}-\dfrac{2}{35}\right)-\dfrac{2}{7}\)

\(=\dfrac{11}{11}+\dfrac{10}{35}-\dfrac{2}{7}\)

\(=1+\dfrac{2}{7}-\dfrac{2}{7}\)

\(=1\)