A shopkeeper's cash box in Indore holds 26 ten-rupee notes, 14 twenty-rupee notes and 20 fifty-rupee notes. He pulls out one note without looking. What is the probability that the note is worth at least twenty rupees?

Total notes = 26 + 14 + 20 = 60. "At least twenty rupees" means the twenty-rupee and the fifty-rupee notes, i.e. 14 + 20 = 34 notes. $P=\frac{34}{60}=\frac{17}{30}.\frac{13}{30}$ counts the ten-rupee notes, which is the complement; $\frac{1}{3}$ reads "at least" as "more than" and takes only the fifty-rupee notes; $\frac{2}{3}$ adds the two cheapest kinds, 26 + 14 = 40 notes, instead of the two dearest.