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Lời giải:
a.
$23+23\times 45+23\times 44=23\times (1+45+44)=23\times 90$
$=23\times (100-10)=23\times 100-23\times 10=2300-230=2070$
b.
$=36\times 280-36\times 79-36$
$=36\times (280-79-1)=36\times (280-80)=36\times 200=7200$
c.
$=72\times 10+72\times 25+72\times 66-72$
$=72\times (10+25+66-1)=72\times 100=7200$
`@` `\text {Ans}`
`\downarrow`
`23 + 23 \times 45 + 23 \times 44`
`= 23 \times (1+45 + 44)`
`= 23 \times 90`
`= 2070`
`b)`
`36 \times 280 - 9 \times 79 \times 4 - 36`
`= 36 \times 280 - 9 \times 4 \times 79 - 36`
`= 36 \times 280 - 36 \times 79 - 36`
`= 36 \times (280 - 79 - 1)`
`= 36 \times 200`
`= 7200`
`c)`
`8 \times 9 \times 10 + 6 \times 25 \times 12 + 4 \times 18 \times 66 - 2 \times 36`
`= 2 \times 4 \times 9 \times 10 + 6 \times 2 \times 6 \times 25 + 2 \times 2 \times 18 \times 66 - 2 \times 36`
`= 10 \times 2 \times 36 + 36 \times 2 \times 25 + 36 \times 2 \times 66 - 2 \times 36`
`= 36 \times 2 \times (10 + 25 + 66 - 1)`
`= 72 \times 100`
`= 7200`
_____
`c)`
`439 \times 78 - 38 \times 78 - 78`
`= 78 \times (439 - 38 - 1)`
`= 78 \times 400`
`= 31200`
`d)`
`24 \times 13 + 6 \times 89 \times 4 - 2 \times 24`
`= 24 \times 13 + 24 \times 89 - 2 \times 24`
`= 24 \times (13 + 89 - 2)`
`= 24 \times 100`
`= 2400`
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
\(78+23\cdot81-69=78+1863-69\)
\(=1941-69\)
\(=1872\)
\(78+23\cdot\left(81-69\right)=78+23\cdot12\)
\(=78+276\)
\(=354\)
\(\left(78+23\right)\cdot81-69=101\cdot81-69\)
\(=8181-69\)
\(=8112\)
\(\left(78+23\right)\cdot\left(81-69\right)=101\cdot12\)
\(=1212\)
78 x 31 + 78 x 24 + 55 x 22
= 78 x ( 31 + 24 ) + 55 x 22
= 78 x 55 + 55 x 22
= 55 x ( 78 + 22 )
= 55x 100
= 5500
\(=78\cdot64-78\cdot42+78\cdot78\)
\(=78\left(64-42+78\right)\)
\(=78\cdot100\)
\(=7800\)
Xem lại đề bài nha bạn , Chỗ kia phải là 78 sao lại là 98 ạ .
a) 78 x 31 + 78 x 24 + 78 x 17 x 22 x 72
= 78 x ( 31 + 24 + 17) x 22 x 72
= 78 x 72 x 22 x 72
= ( 78 + 22 ) x 72
= 100 x 72
= 7200
=158.5630361 nhé =))))))