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IMAS 2023–2024 Upper Primary — First Round Question 18

IMAS · IMAS 2023–2024 Upper Primary — First Round

Question 18

There are four positive numbers $a,b,c,d$ so that $a\lt b\lt c\lt d$. Which of the following inequalities is INCORRECT?
  1. $\frac1a+\frac1b\gt \frac1c+\frac1d$
  2. $\frac da\gt \frac ad$
  3. $b+\frac1c\lt c+\frac1b$
  4. $\frac1{cd}\gt \frac1{b^2}$
  5. $c+\frac cb\gt b+\frac ad$