The histogram shows the marks scored by 40 students in a test with maximum 30 marks.

What is the ratio of the number of students who scored marks in the class intervals 10 - 15 and 15 - 20 taken together to that of the students in the class intervals 5 - 10 and 25 - 30 taken together?

15 : 13

Number of students scored marks in the class intervals 10 - 15 and 15 - 20  :  number of students scored marks in the class intervals 5 - 10 and 25 - 30 

=  ( 7 + 8 )  :  ( 8 + 5 )

 =    15       :      13