500 + 500 = 1 000

100 + 100 = 200

200 + 200 = 400

2 000 x 20 = 40 000

500 + 500 = 1000

100 + 100 = 200

200 + 200 = 400

2000 x 20 = 40000

x+20 = 500+520

x+20=1020

x+20=1000

x + 20 = 500 + 520

x + 20 = 1020

x        = 1020 - 20

x        = 1000

Số x là số tự nhiên và thỏa mãn x > 12,500 

c. 20 000

c

\(268+500\times2\)

\(=268+1000\)

\(=1268\)

268+500.20

=268+10000

=10268

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

a) ( 72 - 8x9 ) : ( 20 + 21 + 22 + 23 + 24 + 25 )

= ( 72 - 72 ) : ( 20 + 21 + 22 + 23 + 24 + 25 )

= 0 : ( 20 + 21 + 22 + 23 + 24 + 25 )

= 0

b) ( 500 x 9 - 250 x 18 ) x ( 1 + 2 + 3 + ... + 9 )

= ( 250 x 2 x 9 - 250 x 18 ) x ( 1 + 2 + 3 + ... + 9 )

= ( 250 x 18 - 250 x 18 ) x ( 1 + 2 + 3 + ... + 9 )

= 0 x ( 1 + 2 + 3 + ... + 9 )

= 0

c ) ( 11 + 13 + 15 + ... + 19 ) x ( 6 x 8 - 48 )

= ( 11 + 13 + 15 + ... + 19 ) x ( 48 - 48 )

= ( 11 + 13 + 15 + ... + 19 ) x 0

= 0

a) ( 72 - 8x9 ) : ( 20 + 21 + 22 + 23 + 24 + 25 )

= ( 72 - 72 ) : ( 20 + 21 + 22 + 23 + 24 + 25 )

= 0 : ( 20 + 21 + 22 + 23 + 24 + 25 )

= 0

k) 4 x 113 x 25 - 5 x 112 x 20

= (4 x 25) x 113 - (5 x 20) x 112

= 100 x 113 - 100 x 112

= 100 x (113 - 112)

= 100

p) 1235 x 6789 x (630 - 315 x 2) : 1996

= 1235 x 6789 x (630 - 630) : 1996

= 1235 x 6789 x 0 : 1996

= 0

l) 54 x 113 + 45 x 113 + 113

= 113 (54 + 45 + 1)

= 113 x 100

= 11300

u) (500 x 9 - 250 x 18) x (1 + 2 + 3 + ... + 9)

= (2 x 250 x 9 - 250 x 2 x 9) x (1 +2 + 3 + ... + 9)

= 0 x (1 + 2 + 3 + ... + 9)

= 0

280:20=14

9500:500=19

64000:400=160

102000:600=170