NIMCET 2020 Mathematics PYQ — If , , are three non-zero vectors with no two of which are collin… | Mathem Solvex | Mathem Solvex
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NIMCET 2020 — Mathematics PYQ
NIMCET | Mathematics | 2020
If a, b, c are three non-zero vectors with no two of which are collinear, a+2b is collinear with c and b+3c is collinear with a, then ∣a+2b+6c∣ will be equal to
Choose the correct answer:
A.
Zero
(Correct Answer)
B.
9
C.
1
D.
None
Correct Answer:
Zero
Explanation
Cocept: If a vector A is collinear to other vector B, it can be written as: A=λ×B where λ is any scalar number
Calculation:
Given a+2b is collinear with c ⇒a+2b=λ1×c …(i)
Also given b+3c is collinear with a ⇒b+3c=λ2×a …(ii)
Subtracting 2×(ii) from (i) ⇒a−6c=λ1c−2λ2a ∴λ1=−6, λ2=21
From (ii) ⇒b+3c=−21a ⇒2b+6c=−a ⇒a+2b+6c=0 ⇒∣a+2b+6c∣=0
Explanation
Cocept: If a vector A is collinear to other vector B, it can be written as: A=λ×B where λ is any scalar number
Calculation:
Given a+2b is collinear with c ⇒a+2b=λ1×c …(i)
Also given b+3c is collinear with a ⇒b+3c=λ2×a …(ii)
Subtracting 2×(ii) from (i) ⇒a−6c=λ1c−2λ2a ∴λ1=−6, λ2=21
From (ii) ⇒b+3c=−21a ⇒2b+6c=−a ⇒a+2b+6c=0 ⇒∣a+2b+6c∣=0