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a) 81 + 35 + 19 = (81 + 19) + 35
= 100 + 35
= 135
b) 78 + 65 + 135 + 22 = (78 + 22) + (65 + 135)
= 100 + 200
= 300
a) \(\left(81+19\right)+35=135\)
b) \(\left(78+22\right)+\left(65+135\right)=100+200=300\)
c) \(\left(234+17716\right)+23=17950+23=17973\)
d) \(\left(99+1\right)+85=100+85=185\)
a: =100x26=2600
b: =78x10=780
c: =67x100=6700
d: =1000x575=575000
\(4\times26\times25=\left(4\times25\right)\times26=100\times26=2600\\ 63\times78-53\times78=\left(63-53\right)\times78=10\times78=780\\ 67\times92+67\times8=67\times\left(92+8\right)=67\times100=6700\\ 8\times23\times25\times125=\left(8\times125\right)\times\left(23\times25\right)=1000\times575=57500\)
a) 96 + 78 + 4 = 96 + 4 + 78 = 100 + 78 = 178
67 + 21 + 79 = 67 + 100 = 167
408 + 85 + 92 = 405 + 92 + 85 = 500 + 85 = 585
b) 789 + 285 + 15 = 789 + 300 = 1089
448 + 594 + 52 = 448 + 52 + 594 = 500 + 594 = 1094
677 + 969 + 123 = 677 + 123 + 969 = 1769
a) 96 + 78 + 4 = 96 + 4 + 78 = 100 + 78 = 178
67 + 21 + 79 = 67 + 100 = 167
408 + 85 + 92 = 405 + 92 + 85 = 500 + 85 = 585
b) 789 + 285 + 15 = 789 + 300 = 1089
448 + 594 + 52 = 448 + 52 + 594 = 500 + 594 = 1094
677 + 969 + 123 = 677 + 123 + 969 = 1769
= ( 11 + 89 ) + ( 22 + 78 ) + ( 33 + 67 ) + ( 44 + 56 ) + 55
= 100 + 100 + 100 + 100 + 55
= 400 + 55
= 455
HT
phuonglebao9@gmail.com
=<89+11>+<78+22>+<67+33>+<56+44>+55
=100+100+100+100+55
=400+55
=455
a) 72 + 9 + 8 = ( 72 + 8 ) + 9
= 80 + 9
= 89
b)37 + 18 + 3 = ( 37 + 3 ) + 18
= 40 + 18
= 58
c) 48 + 26 + 4 = 48 + (26 + 4)
= 48 + 30
= 78
d)85 + 99 + 1 = 85 + ( 99 + 1 )
= 85 + 100 = 185
e) 67 + 98 + 33 = ( 67 + 33 ) + 98
= 100 + 98 = 198
Lời giải:
$1+2+3+....+25$
$=(1+25)+(2+24)+(3+23)+(4+22)+(5+21)+(6+20)+(7+19)+(8+18)+(9+17)+(10+16)+(11+15)+(12+14)+13$
$=\underbrace{26+26+26+...+26}_{12}+13$
$=26\times 12+13=325$
a: \(57\cdot78+43\cdot78\)
\(=78\left(57+43\right)\)
\(=78\cdot100=7800\)
b: \(235\cdot67-67\cdot135\)
\(=67\left(235-135\right)\)
\(=67\cdot100=6700\)
c: \(826\cdot19+174\cdot19\)
\(=19\left(826+174\right)\)
\(=19\cdot1000=19000\)
d: \(1634\cdot45-634\cdot45\)
\(=45\left(1634-634\right)\)
\(=45\cdot1000=45000\)
kaka