The median of 80 observations given in the following table is 138. Find the values of 'a' and 'b'. Class Interval…

CBSE Class 10 Maths PYQ · Statistics · Find Freuency · 5 Marks · July 2025 · Standard

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775 Marks · July 2025 · Standard

The median of 80 observations given in the following table is 138. Find the values of 'a' and 'b'.
Class Interval
Frequency
65-85
5
85-105
a
105-125
13
125-145
20
145-165
b
165-185
10
185-205
7

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Correct table
$55 + a + b = 80$
$\Rightarrow a + b = 25$
Median class is 125 – 145
Median = 138
$\therefore 125 + \left(\frac{80}{2} - (18+a)\right) \times \frac{20}{20} = 138$
$\Rightarrow a = 9$
and $b = 16$