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Lời giải:
$3,8\times 2+1,9\times 8+7,6\times 2-17,7$
$=1,9\times 2\times 2+1,9\times 8+1,9\times 4\times 2-17,7$
$=1,9\times 4+1,9\times 8+1,9\times 8-17,7$
$=1,9\times (4+8+8)-17,7$
$=1,9\times 20-17,7=38-17,7=20,3$
\(0,5\times40\times0,2\times20\times0,25\)
\(=\left(0,5\times0,2\right)\times\left(40\times20\times0,25\right)\)
\(=0,1\times200\)
\(=20\)
~ Hok tốt ~
a) \(\left(145\times99+145\right)-\left(143\times102-143\right)\)
\(=\left[145\times\left(99+1\right)\right]-\left[143\times\left(102-1\right)\right]\)
\(=\left(145\times100\right)-\left(143\times101\right)\)
\(=14500-14443\)
\(=57\)
b) \(54\times47-47\times53-20-27\)
\(=47\times\left(54-53\right)-20-27\)
\(=47-20-27\)
\(=0\)
c) \(10000-47\times72-47\times28\)
\(=10000-47\times\left(72+28\right)\)
\(=10000-47\times100\)
\(=10000-4700\)
\(=5300\)
d) \(3457-27\times48-48\times73+6543\)
\(=\left(3457+6543\right)-48\times\left(27+73\right)\)
\(=10000-48\times100\)
\(=10000-4800\)
\(=5200\)
\(72:x=20\)
\(x=72:20\)
\(x=3,6\)
\(57:x=3,8\)
\(x=57:3,8\)
\(x=15\)
\(24:x=4,8\)
\(x=24:4,8\)
\(x=5\)
\(x\times10=8,5\)
\(x=8,5:10\)
\(x=0,85\)
72 : \(\chi\) = 20
\(\chi\) = 72 : 20
\(\chi\) = 3,6
57 :\(\chi\) = 3,8
\(\chi\) = 57 : 3,8
\(\chi\) = 15
24 :\(\chi\) = 4,8
\(\chi\) = 24 : 4,8
\(\chi\) = 5
\(\chi\)x 10 = 8,5
\(\chi\) = 8,5 : 10
\(\chi\) = 0,85
= khong (0)
A=(28,10x128-28,10x78)x(7,6x10-3,8x2x10)
A=(28,10x128-28,10x78)x(7,6x10-7,6x10)
A=(28,10x128-28,10x78)x0
A=0