Our department was discussing whether or not to accept graduate
students whose undergraduate average grade is below the current cutoff
The chairman said: "If we do that, we will lose more than half of our
good ('above-C') students!"
The rector (provost) overruled him, and decided that the department should
accept 1% 'below-C' students.
At the end of the year, the rector said: "What was all the fuss about?
The department accepted 1% below-C students at the beginning of the year,
and by the end of the year the percentage of the above-C students dropped
slightly from 99% to 98%.
What did the chairman say?
The chairman said: "I told you so! We lost more than half of our above-C
And the rector gets a failing, below-C, grade ...
But that is probably just wishful thinking :-)
- Assume that at the beginning of the year 100 students were accepted,
out of which 1 was below-C (1%) and
99 were above-C (99%).
- At the end of the year the percentage of above-C students dropped to 98%,
so their number must have dropped from 99 to 49
(the one below-C student is now 2% of the class, which thus totals only 50).
- So the "slight percentage drop" from 99% to 98% is in fact a big drop
of more than half, from 99 to 49 students!
P.S. This riddle appears in David Gale, Tracking the Automatic Ant,
Springer (1998), page 81