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b, 53.39 + 47.39 - 53.21 - 47.21
= 39( 53 + 47) - 21 53 + 47)
= 39.100 - 21.100
= 100(39 - 21)
= 100. 18
= 1800
bấm cho mình đúng nha ^_^
a)=78.(31+24+17)+22.72
=72.(78+22)
=72.100
=7200
b)=39.(53+47)-21.(53+47)
=100.(39-21)
=100.18
=1800
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P = 78 × 31 + 78 × 24 + 78 × 17 + 22 × 72
P = 78 × (31 + 24 + 17) + 22 × 72
P = 78 × 72 + 22 × 72
P = 72 × (78 + 22)
P = 72 × 100
P = 7200
S = 1 + 1/3 + 1/9 + 1/27 + ... + 1/2187
3S = 3 + 1 + 1/3 + 1/9 + ... + 1/729
3S - S = (3 + 1 + 1/3 + 1/9 + ... + 1/729) - (1 + 1/3 + 1/9 + 1/27 + ... + 1/2187)
2S = 3 - 1/2187
2S = 6560/2187
S = 6560/2187 : 2
S = 6560/2187 × 1/2
S = 3280/2187
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`@` `\text {Ans}`
`\downarrow`
`2023 \times 14 + 2023 \times 83+97`
`= 2023 \times (14+83) + 97`
`= 2023 \times 97 + 97`
`= 196231 +97`
`= 196328`
`78 \times 31+78 \times 24+78 \times 17+78 \times 22 \times 72`
`= 78 \times (31+24+17+22 \times 72)`
`= 78 \times (31+24+17+1584)`
`= 78 \times 1656`
`= 129168`
`371 \times 69+371 \times 14+629 \times 83`
`= 371 \times (69+14) + 629 \times 83`
`= 371 \times 83 + 629 \times 83`
`= 83 \times (371+629)`
`= 83 \times 1000`
`= 83000`
`91 \times 51+49 \times 163-49 \times 72`
`= 91 \times 51 + 49 \times (163-72)`
`= 91 \times 51+49 \times 91`
`= 91 \times (51+49)`
`= 91 \times 100`
`= 9100`
`3 \times 12 \times 17 + 4 \times 9 \times 81 + 2 \times 6 \times 6`
`= 9 \times 4 \times 17 + 4 \times 9 \times 81 + 4 \times 9 \times 2`
`= 9 \times 4 \times (17+81+2)`
`= 36 \times 100`
`= 3600`
`42 \times 17 + 58 \times 83 \times 42 \times 83 + 42 \times 83 + 17`
`= 17 \times (42+58) + 42 \times 83 \times (58 \times 83 +1)`
`= 17 \times 100 + 3486 \times 4815`
`= 1700 + 16785090`
`= 16786790`
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\(\frac{\left(120+60\right)}{12}=\frac{120}{12}+\frac{60}{12}=10+5=15\)
\(78\cdot31+78\cdot17+78\cdot24+22\cdot72=78\left(31+17+24\right)+22\cdot72\)
\(=78\cdot72+22\cdot72=72\left(78+22\right)=72\cdot100=7200\)
\(997+86=997+\left(83+3\right)=\left(997+3\right)+83\)
\(=1000+83=1083\)
\(5\cdot25\cdot2\cdot37\cdot4=\left(5\cdot2\right)\cdot\left(25\cdot4\right)\cdot37\)
\(=10\cdot100\cdot37=37000\)
\(558+336+442+664=\left(558+442\right)+\left(336+664\right)\)
\(=1000+1000=2000\)
5 x 25 x 2 x 37 x 4
= ( 5 x 2 ) x ( 25 x 4 ) x 37
= 10 x 100 x 37
= 1000 x 37
= 37000
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a)1+7+8+15+23+38+61+99+160=412(quy luật là lấy 2 số trước cộng lại được số thứ 3)
b)1+4+5+9+14+23+37+60+97=250(quy luật là lấy 2 số trước cộng lại được số thứ 3)
c)78x31+78x24+78x17+22x72
=78x(31+24+17)+22x72
=78x72+22x72
=72x(78+22)
=72x100
=7200
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a) 2 x 12 x 43 + 3 x 32 x 8 + 25 x 6 x4
=(2 x12) x43+(3 x8) x32+(6 x4) x25
=24 x43+24 x32+ 24 x25
=24 x(43+32+25)
=24 x100
=2400
b) 78 x 31 + 78 x 24 + 17 x 78 + 28 x 78
=78x(31+24+17+28)
=78x100
=7800
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hihi mk giải được 1 đề sau thôi
78x32+78x24+78x17+22x72=78x(32+24+17) +22x72
=78x73+22x72
=5694+1584
=7278
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78x31+78x24+78x17+22x72
=>78x(31+24+17)+22x72
=>78x72+22x72
=>72x(78+22)
=>72x100
=>7200
t nha
12 . 53 + 53 . 16 + 28 . 47
= 53 . ( 12 + 16 ) + 28 . 47
= 53 . 28 + 28 .47
= ( 53 + 47 ) . 48
= 100 . 48
= 4800
78 . 31 . 78 . 24 + 78 . 17 + 22 . 72
= 78 . ( 31 + 24 + 17 ) + 22 . 72
= 78 . 72 + 22 . 72
= ( 78 + 22 ) . 72
= 100 . 72
= 7200
32 x 125 x 3
= 8 . 4 + 125 . 3
= ( 125 . 8 ) . ( 4 . 3 )
= 1000 . 12
= 12000
bang 7178
78 x 31 + 78 x 24 + 78 x 17 + 22 x 71
= 78 x ( 31 + 24 + 17 ) + 22 x 71
= 78 x 72 + 22 x 71
= 78 x ( 71 +1 ) + 22 x 71
= 78 x 71 + 78 x 1 + 22 x 71
= 71 x ( 78 + 22 ) + 78 x 1
= 71 x 100 + 78
= 7100 + 78
= 7178