Answers

2016-03-02T09:54:36+05:30
1:3 = 1x :3x

No. of Girls = 1x
No. of Boys = 3x
Total strength= 40
 
Number of Girls + Number of Boys = Total strength
1x  +  3x  =  40
4x  = 40
x = 40/4 = 10

∴ No. of Girls = 1x = 10
    No. of Boys = 3x = 3(10) = 30
0
And for the graph, take scale:
1 unit = 5 students.