Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
Let A be a 3×3 matrix with detA=4. Let Ri denote the ith row of A. If a matrix B is obtained by performing the operation R22R2+5R3 on 2 A, then detB is equal to :
MathematicsDeterminantsJEE MainJEE Main 2021 (25 Feb Shift 2)
Options:
  • A 64
  • B 16
  • C 128
  • D 80
Solution:
2481 Upvotes Verified Answer
The correct answer is: 64

Let A=a11a12a13a21a22a23a31a32a332A=2a112a122a132a212a222a232a312a322a33

R22R2+5R3

B=2a112a122a134a21+10a314a22+10a324a23+10a332a312a322a33

B=2a112a122a134a21+10a314a22+10a324a23+10a332a312a322a33

B=2a112a122a134a214a224a232a312a322a33+2a112a122a1310a3110a3210a332a312a322a33

B=2×4×2 a11a12a13a21a22a23a31a32a33+2×10×2 a11a12a13a31a32a33a31a32a33

B=16 a11a12a13a21a22a23a31a32a33 +0 

B=16A

Value of the second determinant is zero. Since Row 2 and Row 3 are identical.

|B|=16×4=64|A|=4

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.