9/16=118/.....?
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a) \(39\times118+29\times82\)
\(=39\times2\times59+29\times2\times41\)
\(=2\times\left(39\times59+29\times41\right)\)
\(=2\times\left(2301+1189\right)\)
\(=2\times3490\)
\(=6980\)
b) \(37\times39+78\times14-13\times85-52\times55\)
\(=37\times3\times13+6\times13\times14+13\times85-4\times13\times55\)
\(=13\times\left(37\times3+6\times14+85-4\times55\right)\)
\(=13\times\left(111+84+85-220\right)\)
\(=13\times\left(280-220\right)\)
\(=13\times60\)
\(=780\)
c) \(368:16+752:16+480:16\)
\(=\left(368+752+480\right):16\)
\(=\left(1120+480\right):16\)
\(=1600:16\)
\(=100\)
d) \(5\times11\times18+9\times31\times10+4\times29\times45\)
\(=5\times11\times9\times2+9\times31\times10+2\times2\times29\times5\times9\)
\(=10\times9\times11+10\times9\times31+10\times29\times2\times9\)
\(=90\times11+90\times31+90\times29\times2\)
\(=90\times\left(11+31+29\times2\right)\)
\(=90\times\left(42+58\right)\)
\(=90\times100\)
\(=9000\)
\(\dfrac{4}{9}\cdot\dfrac{35}{118}+\dfrac{5}{9}\cdot\dfrac{35}{118}-\dfrac{35}{118}\\ =\dfrac{38}{118}\left(\dfrac{4}{9}+\dfrac{5}{9}-1\right)\\ =\dfrac{38}{118}\cdot0=0\)
\(\dfrac{4}{9}\cdot\dfrac{35}{118}+\dfrac{5}{9}\cdot\dfrac{35}{118}-\dfrac{35}{118}\)
\(=\dfrac{35}{118}\left(\dfrac{4}{9}+\dfrac{5}{9}-1\right)\)
=0
a, ( 45 + y ) = 278 - 118
( 45 + y ) = 160
y = 160 - 45
y = 115
b, \(2,3y+\frac{1}{2}y-y=9\)
\(y\left(\frac{2}{3}+\frac{1}{2}-1\right)=9\) ( Đến đây bn tự quy đồng nha )
\(y.\frac{1}{6}=9\)
\(y=9:\frac{1}{6}=9.6=54\)
@@ Bài kia bó tay
B = 1 6 + 1 7 + ... + 1 18 + 1 19 = 1 6 + ... + 1 9 + 1 10 + ... + 1 19 < 1 4 + ... + 1 4 ⏟ 4 s + 1 10 + ... + 1 10 ⏟ 10 s = 1 + 1 = 2
B = 1 6 + ... 1 9 + 1 10 + ... + 1 19 < 1 4 + ... + 1 4 ⏟ 4 s o + 1 10 + ... + 1 10 ⏟ 10 s o = 2