Question

Cho biểu thức A và B hãy so sánh :

\(A=\frac{20.30+20.40+40}{72.10+72.18+144}\)

\(B=\frac{60.2+60.8}{30.2+30.8}\)

Answer 1

\(A=\frac{20.30+20.40+40}{72.10+72.18+144}\)                                            \(B=\frac{60.2+60.8}{30.2+30.8}\)

\(A=\frac{20.\left(30+40+2\right)}{72.\left(10+18+2\right)}\)                                                \(B=\frac{60.\left(2+8\right)}{30.\left(2+8\right)}\)

\(A=\frac{20.72}{72.20}=1\)                                                               \(B=\frac{600}{300}=2\)

\(\Rightarrow A< B\)     

Answer 2

\(A=\frac{20.30+20.40+40}{72.10+72.18+144}\)\(=\frac{20.\left(30+40+2\right)}{72.\left(10+18+2\right)}\)\(=\frac{20.72}{72.30}\)=\(\frac{20}{30}=\frac{2}{3}\)

\(B=\frac{60.2+60.8}{30.2+30.8}\)\(=\frac{60.\left(2+8\right)}{30.\left(2+8\right)}\)\(=\frac{60.10}{30.10}=\frac{60}{30}=2\)

Vì \(2>\frac{2}{3}\)nên A < B