tính nhanh =400

tìm x=15

k chomki,mik k lại

tính nhanh :

10 + 20 + 50 + 90 + 100 + 80 + 50

= (10 + 90) + (20 + 80) + (50 + 50) + 100

=      100    +       100    +     100    +  100

=      100 x 4 

=    400

tìm x :

x + 5 = 10 x 2

x + 5 = 20

       x = 20 - 5

       x = 15

tchs mình tch lại

10+20+50+90+100+80+50

=(10+90)+(20+80)+(50+50)+100

=100+100+100+100

=100x4

=400

x+5=10x2

=>x+5=20

=>x=20:5

=>x=4

=10000000000

Hok tốt

k mk nha!!

10000000000

10 x10 =100

20 + 60 + 50 + 80 + 90 + 10 + 50 + 60 x 10

= (20 + 80) + (50 + 50 ) + (90 + 10 ) + 600 + 60

=     100     +      100     +      100     + 660

=              960

=(20+80)+(50+50)+(90+10)+(60*10)+60

=100+100+100+600+60

=960

20 + 60 + 50 + 80 + 90 + 10 + 50 + 60 x 10

= 20 + 60 + 50 + 80 + 90 + 10 + 50 + 600

= ( 20 + 80 ) + ( 50 + 50 ) + ( 90 + 10 ) + 60 + 600

= 100 + 100 + 100 + 60 + 600

= 100 . 3 + 660

= 300 + 660

= 960

\(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}=-5\)

<=> \(\frac{x+10}{90}+1+\frac{x+20}{80}+1+\frac{x+30}{70}+1+\frac{x+40}{60}+1+\frac{x+50}{50}+1=0\)

<=> \(\frac{x+100}{90}+\frac{x+100}{80}+\frac{x+100}{70}+\frac{x+100}{60}+\frac{x+100}{50}=0\)

<=> \(\left(x+100\right)\left(\frac{1}{90}+\frac{1}{80}+\frac{1}{70}+\frac{1}{60}+\frac{1}{50}\right)=0\)

<=> x + 100 = 0 

<=> x = -100

Vậy x = -100

( 50 + 50 ) x 90 + ( 5 + 1000 ) x10 

= 100 x 90 + 1005 x 10

= 900 + 10050

= 10950

( 50 + 50 ) x 90 + ( 5 + 1000 ) x10 = 100 x 90 + 1005 x 10 

900 + 10050 = 10950

( 50 + 50 ) x 90 + ( 5 + 1000 ) x10 = 19050

X x 10 x10 x10 x10 = 40000

X x 10000 = 40000

x = 40000 : 10000

x = 4

4 nha bạn

tk mình mình tk lại

kết quả bằng 4

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