Question

So sánh 18/15 với 12/9

Answer 1

\(\dfrac{18}{15}=\dfrac{18:3}{15:3}=\dfrac{6}{5}\)
\(\dfrac{12}{9}=\dfrac{12:3}{9:3}=\dfrac{4}{3}\)
Ta có: 
Mẫu số chung 2 phân số: 15
\(\dfrac{6}{5}=\dfrac{6*3}{5*3}=\dfrac{18}{15}\)
\(\dfrac{4}{3}=\dfrac{4*5}{3*5}=\dfrac{20}{15}\)
Vì \(18< 20\) nên\(\dfrac{18}{15}< \dfrac{20}{15}\)
Vậy \(\dfrac{18}{15}< \dfrac{12}{9}\)

Answer 2

\(\dfrac{18}{15}=\dfrac{6}{5}=1,2\\ Còn:\dfrac{12}{9}=\dfrac{4}{3}\\ Vì:1,2< \dfrac{4}{3}\Rightarrow\dfrac{18}{15}< \dfrac{12}{9}\)