s1 histogram q

Where did you get 6 from oO

140 is the Total Frequency so you have to get the total Area.

e.g. if 6 is the area of a bar and then they said in the question the frequency for that bar is 140 then

6 = K x 140

But they didnt tell you the frequency for the individual bars just the total frequency

i got 6 as i found class width 12 and times by freq density which was 0.5 and gave 6?

oh sorry my bad didnt look at the histogram properly so

the area of that bar is 6cm^2

and so the Frequency is 12

but you cant do 140/6 cause your doing:

Area of BAR = k x Frequency of the WHOLE graph

the formula works so you do:

Area of BAR = k x Frequency of BAR or
Area of whole GRAPH = k x Frequency of GRAPH

Frequency density = Frequency/Class Width
So for the 78.5 to 90.5 range: We know the F.d. is 0.5 and the C.W is 12
So Frequency= 0.5x12= 6

By working out the area which totals 70. We know that each 'block' equals 140/70=2

So we do 6x2=12 Runners

how did u work out the total area 70?