265+5x2+56x10+56

=265+10+56x10+56

=265+56x(10+10)

=265+56x20

=265+1120

=1385

Tính (9,1 + 10,2 + 11,3 + ...+ 17,9) + 19 = (9,1 + 17,9). 9 : 2 + 19 = 121,5 + 19 = 140,5

Tính Mẫu =  \(\frac{40}{42}.\frac{54}{56}.\frac{70}{72}.....\frac{2650}{2652}=\frac{\left(5.8\right).\left(6.9\right).\left(7.10\right)....\left(50.53\right)}{\left(6.7\right).\left(7.8\right).\left(8.9\right)....\left(51.52\right)}=\frac{\left(5.6.7...50\right).\left(8.9.10....53\right)}{\left(6.7.8...51\right).\left(7.8.9...52\right)}=\frac{5.53}{51.7}=\frac{265}{357}\)

Vậy \(P=\frac{140,5}{\frac{265}{357}}.\frac{265}{357}=140,5\)

\(=265\left(2+3+2\cdot3\right)-262=265\cdot11-262=2653\)

2653

Tính một cách hợp lí:

a) 2 834 + 275  - 2 833 - 265;

= (2 834 – 2 833) + (275 – 265)

= 1 + 10

= 11

b) (11 + 12 + 13) - (1 + 2 + 3).

= (11 – 1) + (12 – 2) + (13 – 3)

= 10 + 10 + 10

= 30

a) 2834 + 275 - 2833 - 265= 2833+1+275-2833-265=0+1+275-265=11

b) (11 + 12 + 13) - (1 + 2 + 3)=11 + 12 + 13-1-2-3=10+10+10=30

a) 2 834 + 275 - 2 833 - 265

=(275 - 265) + (2 834 - 2 833)

=10 + 1 = 11

b) (11 + 12 +13 ) - (1 + 2 + 3)

= 11 + 12 +13  - 1 - 2 - 3

= (11 - 1) + (12 - 2) +(13 - 3)

=10 +10 +10 =30

a) 608 292 = 600 000 + 8 000 + 200 + 90 + 2

815 036 = 800 000 + 10 000 + 5 000 + 30 + 6

5 240 601 = 5 000 000 + 200 000 + 40 000 + 600 + 1

b)

50 000 + 6 000 + 300 + 20 + 7 = 56 327

800 000 + 2 000 + 100 + 40 + 5 = 802 145

3 000 000 + 700 000 + 5 000 + 90 = 3 705 090

1)

a) -(2+5) = -2 - 5 = -7

b) +(-3+6) = -3 + 6 = 3

c) (-50+3) = -50 + 3 = -47

d) -(-2+3) = 2 - 3 = -1

e) -(10-3) = -10 + 3 = -7

f) -(-3)-(-3+1) = 3 + 3 - 1 = 5

g) (-5)+(-2+10) = -5 - 2 + 10 = 3

2)

a) -50+120+(-150)-20+30

= -(50 + 20) + (120 + 30 - 150)

= -70

b) 265-70+(-65)-30+15

= (265 - 65) - (70 + 30) + 15

= 200 - 100 + 15 = 115

c) -17+185-183+(-85)-63

= (185 - 85) - (183 + 17) - 63

= 100 - 200 - 63 = -163

d) -30+60+(-170)-260+19

= -(170 + 30) - (260 - 60) + 19

= -200 - 200 + 19 = -381

1/2×(2×x-3)+105/2=-137/2

1/2×(2×x-3)=-137/2-105/2

1/2×(2×x-3)=-242/2

2×x-3=-242/2:1/2

2×x-3=-242

2.x=(-242)+3

2.x=239

x=239:2

x=239/2

A,-12×25-25×75-25×13

=[(-12)-75-13].25

=(-100).25

-2500

B,-50/7×49/10-35/2×-10/7+ -25/3× -9/5

=(-35)-(-25)+(-13)

=-23

C,-354+265-156+125

=[(-354)-156]+(265+125)

=(-510)+277

=-233

D,-74+40-50+16-35

=(-74)+40+(-50)+16+(-35)

=[(-74)+(-35)]+[40+(-50)+16]

=(-109)+26

=-83

E,-2/3×4/5+-4/5×4/3-0,125

=-2/3.4/5+4/5.(-4/3)-0,125

=4/5.[-2/3+(-4/3)]-0,125

=4/5.(-2)-0,125

=-8/5-0,125

=(-1,6)+(-0,125)

=-1,725