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Friday, 9 October

JEE Main 2023 · MathsMultiple choiceSingle correctMediumCalculation

JEE Main 6 April 2023, Shift 1, Maths Q17

Question 17 of 90 in this shift, Maths question 17 of 30, Section A.

The mean and variance of a set of 15 numbers are 12 and 14 respectively. The mean and variance of another set of 15 numbers are 14 and σ2\sigma^2 respectively. If the variance of all the 30 numbers in the two sets is 13, then σ2\sigma^2 is equal to
  1. (1)12
  2. (2)11
  3. (3)10Official answer
  4. (4)9

Official answer

Option 3

NTA final key.

Chapter
Statistics
Topic
Variance and SD
Idea tested
Combined Variance of Two Sets

Same idea in other shifts

Asked 4× in all
  1. 8 Apr 2026, Shift 2 · Q7A set of four observations has mean 1 and variance 13. Another set of six observations has mean 2 and variance 1. Then, the variance of…EasySingle correct
  2. 11 Apr 2023, Shift 1 · Q18Let sets A and B have 5 elements each. Let the mean of the elements in sets A and B be 5 and 8 respectively and the variance of the…MediumSingle correct
  3. 16 Mar 2021, Shift 2 · Q86Consider the statistics of two sets of observations as follows : Size Mean Variance Observation I 10 2 2 Observation II n 3 1 If the…EasyNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.