The first quartile of the given data is 35. find the value of x.
X 0-20/20-40/40-60/60-80/80-100
F 2 x 8 5 1

The given value of the first quartile is related to the value cumulative

frequency up to the class of the first quartile.

Reasons:

The first quartile is one of the five number summary.

The number of terms, N = 2 + x + 8 + 5 + 1 =16 + x

We have;

Where;

The first quartile, Q₁ = 35

L = 20 in the first quartile class

PCF = The cumulative frequency of the first quartile class = 2 + x

f = The frequency of the quartile class = x

C = The class size = 10

Therefore;

Which gives;

Therefore;

70·x = 25·x + 45

45·x = 45

x = 45 ÷ 45 = 1

Learn more about the five number summary here:

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