Question

This year, the number of our male research students has increased by 20% and the number of female research students has decreased by 20%. We now have one student more than before. Which of the following could be the number of research students in my class now?

Answer 1

Last year's number of boys $B$. Last year's number of girls $G$.

This year $1.2B$ and $0.8G$

$$1.2B+0.8G= B+G+1$$

$$0.2B=1+0.2G$$

$$B=5+G$$

For example $B=10, G=5.$ The number of research students in my class now is

$$10+5+1=16$$

For example $B=20, G=15.$ The number of research students in my class now is

$$20+15+1=36$$