Question

tìm x sao cho 1/5 < x/30 < 1/4

Answer 1

\(\dfrac{1}{5}< \dfrac{x}{30}< \dfrac{1}{4}\\ 30\cdot\dfrac{1}{5}< x< 30\cdot\dfrac{1}{4}\\ 6< x< 7,5\)

Answer 2

\(\frac15<\frac{x}{30}\) < \(\frac14\)

\(\frac{1\times12}{5\times12}\) < \(\frac{x\times2}{30\times2}\) < \(\frac{1\times15}{4\times15}\)

\(\frac{12}{60}\) < \(\frac{2x}{60}\) < \(\frac{15}{60}\)

12 < 2\(x\) < 15

\(\frac{12}{2}\) < \(x<\frac{15}{2}\)

6 < \(x<7,5\)

Vậy 6 < \(x<7,5\)