B. 40
Feedback Step (i) Let x be the number of boys and y be the number of girls.
Given total number of boys and girls = 100
x+y=100
Step (ii) A boy gets Rs. 3.60 and a girl gets Rs. 2.40
The amount given to 100 boys and girls = Rs. 312
3.6x+2.4y=312
Step (iii)
Solving (i) and (ii)3.6x+3.6y=360 multiplying by 3.6
3.6x+2.4y1.20yy=312=48=40
The number of girls is 40.