ok let me explain...
first things first... u should know this FREQUENCY = HEIGHT X CLASS WIDTH, ok?
lets take the given example...
freq=115
class width=2
with the help of the formula, height= 115/2
=57.5
now the height (freq. density) SHOULD equal 57.5, but it doesnt..
it equals 11.5 cm..
now u will have to find the "FACTOR'' by which the height is reduced..
11/57.5 which equals 0.2, ok?
now find the supposed height of the other column..
(example..3rd column...)
height = 26/2 = 13...
now multiply 13 into the factor...
13*0.2 = 2.6!
there you go...
same thing with other columns....
if u dont get me, please notify,, i will try again