x + ( x + 1 ) + ( x + 2 ) + .................. + ( x+ 25 ) = 1235
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x+(x+1)+(x+2)+....+(x+25)=1235
= \(\left(x+x+...+x\right)+\left(1+2+3+...+25\right)=1235\)
= \(26x+325=1235\)
=> \(26x=1235+325=1560\)
= \(26x=1560\)
=> x = 1560 : 26 = 60
=> x = 60
x + (x+1) + (x+2) + ...+ (x+25 ) = 1235
x + x + 1 + x + 2 +...+ x + 25 = 1235
(x + x + x +...+ x) + (1 + 2 +...+ 25) = 1235
26x + 325 = 1235
26x = 1235 - 325 = 910
x=910:26=35
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
a: =24*1000=24000
b: =120*1000=120000
c: =72(135+65):25-140
=72*8-140=436
d: =18(957-354-621):72=-9/2
1235×9–2470×2+1235×5
=1235×9–1235×2×2+1235×5
=1235×9–1235×4+1235×5
=1235×(9−4+5)
=1235×10
=12350
a) \(30\times1235\times4-8\times235\times15\)
\(=120\times1235-120\times235\)
\(=120\times\left(1235-235\right)\)
\(=120\times1000\)
\(=120000\)
b) \(\left(120\times99+120\right)-185\times101+185\)
\(=120\times\left(99+1\right)-185\cdot\left(101-1\right)\)
\(=120\times100-185\times100\)
\(=12000-18500\)
\(=-6500\)
a) 30 x 1235 x 4 - 8 x 235 x 15
=(30x4) x 1235 - (8x15)x235
= 120 x 1235 - 120 x 235
=120 x (1235-235)
=120 x 1000
=120000
b) ( 120 x 99 +120) - 185 x 101-185
=(120 x 99 + 120) - (185x101+185)
=120x(99+1) - 185x(101+1)
=120 x 100-185x102
=12000-18870
= -(18870-12000)
= -6870
\(1235\text{×}6789\text{×}\left(630-315\text{×}2\right)\)
\(=1235\text{×}6789\text{×}\left(630-630\right)\)
\(=1235\text{×}6789\text{×}0=0\)
\(\left(100+67\right)\text{×}67+\left(200-38\right)\text{×}33\)
\(=167\text{×}67+167\text{×}33\)
\(=167\text{×}\left(67+33\right)\)
\(=167\text{×}100=16700\)
\(72+36\text{×}2+24\text{×}3+18\text{×}4+12\text{×}2+168\)
\(=72+72+72+72+24+168\)
\(=\left(72\text{×}4\right)+24+168=288+24+168=480\)
a)
x − 345 = 1235 x = 1235 + 345 x = 1580
b)
x × 28 = 312 × 14 x × 28 = 4368 x = 4368 : 28 x = 156
=26x + ( 1+ 2+....+25) = 1235
=26x + 325 = 1235
=26x = 910
suy ra x =35
bn có thể trình bày ( 1+2+3 +...+25 rõ ràng hơn