6. Gill is now 28 years old and is a teacher of Mathematics at a school which has 600 pupils. There are 30 more girls than boys at the school.
How many girls are at Gill's school?
A 270
В 300
C 315
D 330
E 345
6. C Let there be $g$ girls in Gill's school. Then there are $(g-30)$ boys at the school. So $g+g-30=600$. Therefore $2 g=630$, that is $g=315$.