a) 2 100 : 10 = 210

    4 500 : 100 = 45

    83 000 : 1 000 = 83

b) 720 : 10 : 8 = 72 : 8 = 9

    1 500 : (5 x 100) = 1 500 : 5 : 100 = 300 : 100 = 3

    60 000 : 1 000 x 6 = 60 x 6 = 360

a)1700

b)2000

a, 500+500+500+(100 x 2)

=500 x 3+ 100x2

=1500+200

=1700

b, 700+300+(100 x 10)=700+300+1000=1000+1000=2000

k minh nha

a) = 1700

b) =2000

a) x . x . x = 125

x³ =125

x³ = 5³

= > x = 5

b) ( x + 500 ) = 1000 - 200 . 2

x + 500 = 1000 - 400

x + 500 = 600

x = 600 - 500

x = 100

c) [( x + 10 ) . 100 ] = 500 + 500 . 10

( x + 10 ) . 100 = 500 + 5000

( x + 10 ) . 100 = 5500

x + 10 = 5500 : 100

x + 10 = 55

x = 55 - 10

x = 45

D

D

D

\(\frac{1}{1\times10}+\frac{1}{2\times15}+\frac{1}{3\times20}+...+\frac{1}{98\times495}+\frac{1}{99\times500}\)

\(=\frac{1}{1\times2\times5}+\frac{1}{2\times3\times5}+\frac{1}{3\times4\times5}+...+\frac{1}{98\times99\times5}+\frac{1}{99\times100\times5}\)

\(=\frac{1}{5}\times\left(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{98\times99}+\frac{1}{99\times100}\right)\)

\(=\frac{1}{5}\times\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\right)\)

\(=\frac{1}{5}\times\left(1-\frac{1}{100}\right)=\frac{1}{5}\times\frac{99}{100}=\frac{99}{500}\)

\(\frac{1}{1\times10}+\frac{1}{2\times15}+\frac{1}{3\times20}+...+\frac{1}{98\times495}+\frac{1}{99\times500}\)

\(=\frac{1}{1\times2\times5}+\frac{1}{2\times3\times5}+\frac{1}{3\times4\times5}+...+\frac{1}{98\times90\times5}+\frac{1}{90\times100\times5}\)

\(=\frac{1}{5}\times\left(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{98\times99}+\frac{1}{99\times100}\right)\)

\(=\frac{1}{5}\times\left(\frac{2-1}{1\times2}+\frac{3-2}{2\times3}+...+\frac{99-98}{98\times99}+\frac{100-99}{99\times100}\right)\)

\(=\frac{1}{5}\times\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\right)\)

\(=\frac{1}{5}\times\left(1-\frac{1}{100}\right)=\frac{99}{500}\)

cảm ơn bạn Xyz và bạn Đoàn Đức Hà nhìu (^-^) thank you !!!!!!!!!!!!!!!!!

Tìm x :

[ 500 : (x - 10) x 2 ] + 100 = 200

=>       500 : ( x - 10 ) x 2 = 200 - 100

=>       500 : ( x - 10 ) x 2 = 100

=>             500 : ( x - 10 ) = 100 : 2

=>             500 : ( x - 10 ) = 50

=>                         x - 10 = 500 : 50

=>                         x - 10 = 10

=>                                x = 10 + 10

=>                                x = 20

                                  Vậy x= 20 

[500 : (x-10) x 2] + 100 = 200

500 : (x-10) x 2 = 100

=> 500 : (x-10) = 50

=> x - 10 = 10

=> x =20

a,

36 x 40 = (36 x 4) x 10 = 144 x 10 = 1 440

72 x 60 = (72 x 6) x 10 = 432 x 10 = 4 320

89 x 50 = (89 x 5) x 10 = 445 x 10 = 4 450

b,

450 x 70 = (45 x 7) x 100 = 315 x 100 = 31 500

2300 x 500 = (23 x 5) x 10 000 = 115 x 10 000 = 1 150 000

17 000 x 30 = (17 x 3) x 10 000 = 510 000

26,28 : 10% x 8,5 + 262,8 x 6,5 - 2,628 x 500

= 2628

#HT

thiếu