Tính nhanh
a 23 .75 + 23.75 +180
b 27.76+24.27 +260
c 2.53 -36: 32+ 2.3
d 15 .23+4.32 5.7
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\(\dfrac{7}{19}x\dfrac{8}{23}+\dfrac{7}{19}x\dfrac{15}{23}+1\dfrac{7}{19}\)
= \(\dfrac{7}{19}x\left(\dfrac{8}{23}+\dfrac{15}{23}\right)+1+\dfrac{7}{19}\)
=\(\dfrac{7}{19}x1+1+\dfrac{7}{19}\)
= \(\dfrac{7}{19}+1+\dfrac{7}{19}=1\dfrac{14}{19}\) = \(\dfrac{33}{19}\)
\(\dfrac{75}{100}+\dfrac{18}{21}+\dfrac{49}{32}+\dfrac{1}{4}+\dfrac{3}{21}-\dfrac{17}{32}\)
= \(\dfrac{3}{4}+\dfrac{6}{7}+\dfrac{49}{32}+\dfrac{1}{4}+\dfrac{1}{7}-\dfrac{17}{32}\)
= \(\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\left(\dfrac{6}{7}+\dfrac{1}{7}\right)+\left(\dfrac{49}{32}-\dfrac{17}{32}\right)\)
= 1 + 1 + 1 = 3
\(\dfrac{8}{9}x\dfrac{15}{16}x\dfrac{24}{25}x\dfrac{35}{36}x\dfrac{48}{49}x\dfrac{63}{64}\)
= \(\dfrac{3}{4}\) *Câu này bạn tự sử dụng gạch nhé!
`1,`
`a,`
`7/19 \times 8/23 + 7/19 \times 15/23 + 1 7/19`
`= 7/19 \times 8/23 + 7/19 \times 15/23 + 1 + 7/19`
`= 7/19 \times (8/23 + 15/23 + 1) + 1`
`= 7/19 \times 2 + 1`
`=14/19 + 1`
`= 33/19`
`b,`
`75/100 + 18/21 + 49/32 + 1/4 + 3/21 - 17/32`
`= 75/100 + (18/21 + 3/21) + (49/32 - 17/32) + 1/4`
`= 0,75 + 1 + 1 + 0,25`
`= (0,75 + 0,25) + 1 + 1`
`= 1+1+1=3`
`c,`
`8/9 \times 15/16 \times 24/25 \times 35/36 \times 48/49 \times 63/64`
`=` \(\dfrac{2\times3}{3\times3}\times\dfrac{3\times5}{4\times4}\times\dfrac{3\times4\times2}{5\times5}\times\dfrac{5\times7}{6\times6}\times\dfrac{6\times8}{7\times7}\times\dfrac{7\times9}{8\times8}\)
`= 3/4` (bạn sử dụng gạch, rút gọn các số là được nhé).
\(27.77+24.27-27\)
\(=27.\left(77+24-1\right)\)
\(=27.100\)
\(=2700\)
\(174\div\left\{2\left[36+\left(4^2-23\right)\right]\right\}\)
\(=174\div\left\{2\left[36+\left(16-23\right)\right]\right\}\)
\(=174\div\left\{2\left[36+\left(-7\right)\right]\right\}\)
\(=174\div\left\{2.29\right\}\)
\(=174\div58\)
\(=3\)
\(3^2.4-\left[30-\left(5-2\right)^2\right]\)
\(=9.4-\left[30-3^2\right]\)
\(=36-\left[30-9\right]\)
\(=36-21\)
\(=15\)
`a,`
`31/23-(7/32+8/23)`
`=31/23-7/32-8/23`
`=(31/23-8/23)-7/32`
`=1-7/32=25/32`
`b,`
`38/45-(8/45-17/51-3/11)`
`=38/45-8/45+17/51+3/11`
`= (38/45-8/45)+17/51+3/11`
`=2/3+17/51+3/11`
`=1+3/11=14/11`
`c,`
`(1/3+12/67+13/41)-(79/67-28/41)`
`= 1/3+12/67+13/41-79/67+28/41`
`= 1/3+(12/67-79/67)+(13/41+28/41)`
`= 1/3+(-1)+1=1/3+(-1+1)=1/3+0=1/3`
`d,`
`1/5+(-1/6)+1/7+(-1/8)+1/9+1/8+(-1/7)+1/6+(-1/5)`
`= (1/5+ -1/5)+(-1/6+1/6)+(1/7+ -1/7)+(-1/8 +1/8)+1/9`
`= 0+0+0+0+1/9=1/9 .`
\(a.415\times7-415\times5+415\times8\)
\(=415\times\left(7-5+8\right)=415\times10=4150\)
\(b.23\times87+12\times23+23\)
\(=23\times\left(87+12+1\right)=23\times100=2300\)
a. 415 x 7 - 415 x 5 + 4 15 x 8
= 415 x ( 7 - 5 + 8 )
= 415 x 10
= 41 50
b. 23 x 87 + 1 2 x 23 + 2 3
= 23x 87 + 12 x 23 + 23 x 1
= 23 x ( 87 + 12 + 1 )
= 23 x 100
= 2300
=
\(\frac{24.27-23}{24+47.23}=\frac{648-23}{24+1081}=\frac{625}{1105}=\frac{125}{221}\)
_Học_tốt_
=^.^=