The chart above describes departures from a certain airport on a certain day. If 1200 flights were delayed, how many flights departed on time?
(a)250
(b)300
(c)350
(d)400
Answer
Answer (as printed): D
Explanation
Percentage of delayed flights $=(43+17+12+3) \%=75 \%$. Percentage of on-time flights $=(100-75) \%=25 \%$. Let the total number of flights be $x$. Then, $75 \%$ of $x=1200 \Rightarrow x=\left(\frac{1200 \times 100}{75}\right)=1600$. $$\text { ∴ Number of on-time flights }=25 \% \text { of } 1600=400 .$$
Explanation as extracted from the printed page; notation may be imperfect.