Tính hợp lý :
12 x 78 - 24 x19
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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`
a) (-124) + 24 = -100
b) 37. 78 + 37. 22
= 37 . ( 78 + 22 )
= 37 . 100
= 3700
78.31+78.68+78
=78.31+78.68+78.1
=78.(31+68+1)
=78.100
=7800
1024:(22.7+22.25)
=1024:[22.(7+25)]
=1024:128
=8
24-[20-(5-1)2]
=24-[20-42]
=24-[20-16]
=24-4
=20
x3=64
=>x3=43
=>x=4
2x+1=128
2x.21=128
2x=128:2
2x=64
2x=26
=>x=6
1) 12 x 19 + (3 x 4) x 24 - (6 x 2) x 33
= 12 x19 + 12 x 24 -12 x 33
= 12 x (19 + 24 - 33)
= 12 x 10
=120
2) 35 x1001-35
=35 x (1001 - 1)
= 35 x 1000
= 35 000
1) 12 x 19 + (3 x 4) x 24 - (6 x 2) x 33
= 12 x19 + 12 x 24 -12 x 33
= 12 x (19 + 24 - 33)
= 12 x 10
=120
2) 35 x1001-35
=35 x (1001 - 1)
= 35 x 1000
= 35 000
-1 ≤ x ≤ 5 mà x ∈ Z. Do đó: x ∈ { -1 ; 0 ; 1 ; 2 ; 3 ; 4 ; 5 }
\(1\frac{13}{15}.0,75-\left(\frac{104}{195}+25\%\right).\frac{24}{47}-3\frac{12}{13}:3\)
\(=\frac{28}{15}.\frac{3}{4}-\left(\frac{8}{15}+\frac{1}{4}\right).\frac{8}{9}-\frac{51}{13}.\frac{1}{3}\)
\(=\frac{7}{5}-\left(\frac{32}{60}+\frac{15}{60}\right).\frac{8}{9}-\frac{17}{13}\)
\(=\frac{7}{5}-\frac{47}{60}.\frac{8}{9}-\frac{17}{13}\)
\(=\frac{7}{5}-\frac{94}{135}-\frac{17}{13}\)
\(=\frac{-212}{351}\)
Tự quy đồng
\(2\frac{3}{4}.\left(-0,4\right)-1\frac{3}{5}.2,75+\left(-1,2\right):\frac{4}{11}\)
\(=\frac{11}{4}.\frac{-2}{5}-\frac{8}{5}.\frac{11}{4}-\frac{6}{5}.\frac{11}{4}\)
\(=\frac{11}{4}.\left(\frac{-2}{5}-\frac{8}{5}-\frac{6}{5}\right)\)
\(=\frac{11}{4}.\frac{-16}{5}\)
\(=\frac{-44}{5}=-8\frac{4}{5}\)
12 x 78 - 24 x 19
= 12 x 78 - 12 x 2 x 19
= 12 x 78 - 2 x 19
= 12 x 78 - (2 x 9)
= 12 x 78 - 38
= 12 x (78 - 38)
= 12 x 40
= 480
12x78-24x19
=12x78-12x(2x19)
=12x78-12x38
=12x(78-38)
=12x40
=480