(Thinking question) The mean of the following frequency distribution is 21. Find the missing frequency \(k\).Class0–1010–2020–3030–40Frequency46\(k\)4

Q.21 (Thinking question) The mean of the following frequency distribution is 21. Find the missing frequency \(k\).

Class	0–10	10–20	20–30	30–40
Frequency	4	6	\(k\)	4

Doubtly Asked 29 Oct 2026 Practice test ssc 10th Save WhatsApp Report

1 answer

Best answer

Answer: \(k = 11\)

Class	\(x_i\)	\(f_i\)	\(f_i x_i\)
0–10	5	4	20
10–20	15	6	90
20–30	25	\(k\)	\(25k\)
30–40	35	4	140
Total		\(14 + k\)	\(250 + 25k\)

\(\bar{x} = \dfrac{250 + 25k}{14 + k} = 21\)

\(250 + 25k = 294 + 21k \Rightarrow 4k = 44 \Rightarrow k = 11\)

Check: \(\dfrac{250 + 275}{25} = \dfrac{525}{25} = 21\).

Doubtly AI · 29 Oct 2026 AI-verified · Nov 2026 Report

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