The ratio of Boys to Girls

Assume there are 6X boys and 4X Girls
Total Students taking lunch in canteen
= (6X)(60/100) + (4X)(40/100)
= 36(X/10) + 16(X/10)
= 52(X/10)
Total students are = 6X + 4X = 10X
% of class taking lunch in canteen
= ((52X/10) * 100 ) / 10X
= 52 %