JEE Main 2025 · MathsMultiple choiceSingle correctEasyCalculation

JEE Main 7 April 2025, Shift 1, Maths Q9

Question 9 of 75 in this shift, Maths question 9 of 25, Section A.

The mean and standard deviation of 100 observations are 40 and 5.1, respectively. By mistake one observation is taken as 50 instead of 40. If the correct mean and the correct standard deviation are

\mu

and

\sigma

respectively, then

10(\mu + \sigma)

is equal to

(1) $451$
(2) $449$ Official answer
(3) $447$
(4) $445$

Official answer

Option 2

NTA final key.

Chapter: Statistics
Topic: Variance and SD
Idea tested: Correcting Incorrect Variance

Same idea in other shifts

Asked 3× in all

8 Apr 2023, Shift 2 · Q18Let the mean and variance of 12 observations be $\frac{9}{2}$ and $4$ respectively. Later on, it was observed that two observations were…MediumSingle correct
13 Apr 2023, Shift 2 · Q29The mean and standard deviation of the marks of 10 students were found to be 50 and 12 respectively. Later, it was observed that two marks…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.