This is a very good question which can be solved by simple calculations and pure logic. Beware of the trick element though, which can get you into trouble. Answer option E seems to be a very common trap answer, therefore.
The class has a total of 16 students, all of whom have distinct heights. The question mentions 1/5th of the boys and 1/3rd of the girls. This is a clear indication that the number of boys and girls should be multiples of 5 and 3 respectively. The only possible combination turns out to be 10 boys and 6 girls.
Therefore, as per the question, 2 boys are shorter than the shortest girl and 2 girls are taller than the tallest boy.
Let the shortest girl be Q and the tallest boy be M. Then, the entire question can be represented diagrammatically, like this:
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08th June 2019 - Reply 1.JPG [ 21.85 KiB | Viewed 22216 times ]
The 2 boys who are shorter than the shortest girl will be shorter than the other girls too. Similarly, the 2 girls who are taller than the tallest boy will be taller than the other boys too.
How many boys are we left with who are taller than the shortest girl? 8, correct? But one of these 8 boys is M himself. So,
there are 7 boys taller than the shortest girl, but shorter than the tallest boy.
How many girls are shorter than the tallest boy? 4, right? But, one of these 6 girls is Q herself. So,
there are 3 girls who are shorter than the tallest boy but taller than the shortest girl.In all, we have 10 students in between Q and M. 10 as a percentage of 16 is nothing but
\(\frac{10}{16}\) * 100 = 62.5%
So, the correct answer option is C.
If you forget to exclude M and Q from your calculation, you will end up marking 75% as the answer, which as we mentioned, could be a very common trap answer in this question.
Hope this helps!