Find the mode of data:

Marks obtained	25-35	35-45	45-55	55-65	65-75	75-85
No. of students	7	31	33	17	11	11

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We have to find the mode of the given data.

The maximum frequency of the given data is 33 and the corresponding class is 45-55. So, 45-55 is the modal class.

Therefore,

$l = 45, h = 10, f = 33, f_1=31, f_2=17$

Mode $= l +[\frac{f-f_1}{2f-f_1-f_2}]\times h$

$= 45+[\frac{33-31}{2(33)-31-17}]\times 10$

$=45+[\frac{2}{66-48}]\times10$

$=45+\frac{2}{18}\times10$

$=45+1.1$

$=46.1$