Nội dung bài giảng
Bài 60. Tìm \(x\) trong các tỉ lệ thức sau:
a) \(\left( {{1 \over 3}x} \right):{2 \over 3} = 1{3 \over 4}:{2 \over 5}\)
b) \(4,5:0,3 = 2.25:(0,1.x)\)
c) \(8:\left( {{1 \over 4}x} \right) = 2:0,02\)
d) \(3:2{1 \over 4} = {3 \over 4}:(6.x)\)
Lời giải:
a) \(\left( {{1 \over 3}x} \right):{2 \over 3} = 1{3 \over 4}:{2 \over 5}\)
\(\Rightarrow{x \over 3}:{2 \over 3} = {7 \over 4}:{2 \over 5} \Rightarrow {x \over 3}.{3 \over 2} = {7 \over 4}.{5 \over 2}\)
\(\Rightarrow {x \over 2} = {{35} \over 8} \Rightarrow x = {{35.2} \over 8} = {{35} \over 4}\)
b) \(4,5:0,3 = 2.25:(0,1.x)\)
\( \Rightarrow 0,1x = {{2,25.0,3} \over {4,5}}\)
\(\Rightarrow 0,1x = 0,15 \Rightarrow x = 1,5\)
c) \(8:\left( {{1 \over 4}x} \right) = 2:0,02\)
\(\Rightarrow {1 \over 4}x = {{8.0,02} \over 2} \)
\(\Rightarrow {1 \over 4}x = 0,08 \Rightarrow x = 0,32\)
d) \(3:2{1 \over 4} = {3 \over 4}:(6.x)\)
\( \Rightarrow 3.{4 \over 9} = {3 \over {4.6x}} \Rightarrow {4 \over 3} = {1 \over {8x}}\)
\(\Rightarrow 8x = {{3.1} \over 4} \Rightarrow 8x = {3 \over 4}\)
\(\Rightarrow x = {3 \over {32}}\)