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\(...=25x4x\left(7x3+3x4x5+2\right)=100x\left(21+120+2\right)=100x143=14300\)
7 x 12 x25 +3 x 16 x125 +8 x25
=7 x4 x3 x25 +3 x4 x4 x5 x25+4x2x25
=(4 x25) x(7 x3 +3 x4 x5 +2)
= 100 x (21 +60 +2)
= 100 x 83
= 8300
\(A=\frac{18\times123+9\times567\times2+3\times310\times6}{25\times1,8\times4}\)
\(A=\frac{18\times123+9\times2\times567+3\times6\times310}{25\times4\times1,8}\)
\(A=\frac{18\times123+18\times567+18\times310}{100\times1,8}\)
\(A=\frac{18\times\left(123+567+310\right)}{180}\)
\(A=\frac{18\times1000}{180}\)
\(A=\frac{18000}{180}\)
\(A=100\)
Bài 1:
a; (\(\dfrac{1}{4}\)\(x\) - \(\dfrac{1}{8}\)) x \(\dfrac{3}{4}\) = \(\dfrac{1}{4}\)
\(\dfrac{1}{4}x\) - \(\dfrac{1}{8}\) = \(\dfrac{1}{4}\) : \(\dfrac{3}{4}\)
\(\dfrac{1}{4}\)\(x\) - \(\dfrac{1}{8}\) = \(\dfrac{1}{4}\) x \(\dfrac{4}{3}\)
\(\dfrac{1}{4}x\) - \(\dfrac{1}{8}\) = \(\dfrac{1}{3}\)
\(\dfrac{1}{4}x\) = \(\dfrac{1}{3}\) + \(\dfrac{1}{8}\)
\(\dfrac{1}{4}\) \(x\)= \(\dfrac{8}{24}\) + \(\dfrac{11}{24}\)
\(\dfrac{1}{4}x=\dfrac{11}{24}\)
\(x=\dfrac{11}{24}:\dfrac{1}{4}\)
\(x=\dfrac{11}{24}\times4\)
\(x=\dfrac{11}{6}\)
b; \(\dfrac{12}{5}:x\) = \(\dfrac{14}{3}\) x \(\dfrac{4}{7}\)
\(\dfrac{12}{5}\) : \(x\) = \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{12}{5}\) : \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{12}{5}\) x \(\dfrac{3}{8}\)
\(x\) = \(\dfrac{9}{10}\)
a;
c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)
= \(\dfrac{10+10+10+10+5}{10}\)
= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)
= \(\dfrac{10\times4+5}{10}\)
= \(\dfrac{45}{10}\)
= \(\dfrac{9}{2}\)
Bài 2:
a,4x25x0,25x\(\frac{1}{5}\) x \(\frac{1}{2}\) x 2
=4x25x0,25x0,2x0,5x2
=(4x0,25)+(25x0,2)+(0,5x2)
= 1 + 5 1
=7
X + 1/2 + X + 1/4 + X + 1/8 + X + 1/8 +X +1/16
= X + 8/16 + X + 4/16 + X + 2/16 + X + 2/16 +X + 1/16
= X + ( 8/16 + 4/16 + 2/16 + 2/16 ) + X +1/16
= X + 1 + X + 1/16
= X + ( 1 + 1/16 )
= X + 1 VÀ 1/16
a, 2x3x4x8x25x125= (2x3)x(4x25)x(8x125)= 6x100x1000=600000
b,42/5 +56/9+23/4+3/5+1/3+1/4= (42/5+3/5)+(23/4+1/4)+(56/9+1/3)=9+6+59/9=
a:Sửa đề: 1x3+2x4+...+99x101
\(=1\times\left(1+2\right)+2\times\left(2+2\right)+\cdots+99\times\left(99+2\right)\)
\(=\left(1\times1+2\times2+\cdots+99\times99\right)+2\times\left(1+2+\cdots+99\right)\)
\(=\frac{99\times\left(99+1\right)\times\left(2\times99+1\right)}{6}+2\times\frac{99\times100}{2}\)
\(=\frac{99\times100\times199}{6}+99\times100=33\times50\times199+99\times100\)
\(=33\times50\times\left(199+3\times2\right)=33\times50\times205=338250\)
b: \(\frac89\times\frac{15}{16}\times\ldots\times\frac{2499}{2500}\)
\(=\left(1-\frac19\right)\times\left(1-\frac{1}{16}\right)\times\ldots\times\left(1-\frac{1}{2500}\right)\)
\(=\left(1-\frac13\right)\times\left(1-\frac14\right)\times\ldots\times\left(1-\frac{1}{50}\right)\times\left(1+\frac13\right)\times\left(1+\frac14\right)\times\ldots\times\left(1+\frac{1}{50}\right)\)
\(=\frac23\times\frac34\times\ldots\times\frac{49}{50}\times\frac43\times\frac54\times\ldots\times\frac{51}{50}=\frac{2}{50}\times\frac{51}{3}=\frac{17}{25}\)
\(2\times3\times5+25\times8\times4+70+4\times2\times25\)
\(=15\times2+100\times8+70+100\times2\)
\(=30+800+70+200\)
\(=\left(30+70\right)+\left(800+200\right)\)
\(=100+100\times10\)
\(=100+1000\)
\(=1100\)