JEE Main 2020 · MathsNumerical answerNumerical valueMediumMulti-step

JEE Main 8 January 2020, Shift 1, Maths Q72

Question 72 of 75 in this shift, Maths question 22 of 25, Section B.

The number of all

3\times3

matrices A, with enteries from the set

\{-1,0,1\}

such that the sum of the diagonal elements of

AA^T

is 3, is ______.

Official answer

672.00

NTA final key (Jan 2020).

Chapter: Matrices
Topic: Matrix Multiplication
Idea tested: Trace of A times A Transpose

Same idea in other shifts

Asked 2× in all

26 Feb 2021, Shift 1 · Q73Let A be a symmetric matrix of order 2 with integer entries. If the sum of the diagonal elements of $A^2$ is 1, then the possible number…MediumSingle correct

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 108 of the 174 JEE Main shifts held from 2017 to 2026.