CBSE 2025 · Region 2 · Set 3 · Q24 · 2 marks
If $\displaystyle |\vec{a}|=2,|\vec{b}|=3$ and $\displaystyle \vec{a} \cdot \vec{b}=4$, then evaluate $\displaystyle |\vec{a}+2 \vec{b}|$.
Marking-scheme solution
\[\begin{aligned}
& (\vec{a}+2 \vec{b})^{2}=|\vec{a}|^{2}+|2 \vec{b}|^{2}+4 \vec{a} \cdot \vec{b} \\
& =56 \\
& \Rightarrow|\vec{a}+2 \vec{b}|=\sqrt{56}
\end{aligned}
\]
Vector AlgebraProduct of Two VectorsApplyvery_short_answereasy
More from Vector Algebra
- If a+ b+ c= 0 such that a =3, b =5, c =7, then find the angle between a and b. OR If a and b are unit vectors…2025 · asked 3×
- The position vectors of points P and Q are p and q respectively. The point R divides line segment PQ in the…2024 · asked 3×
- If a+ b= i and a=2 i-2 j+2 k, then b equals:2023 · asked 3×
- A vector a makes equal angles with all the three axes. If the magnitude of the vector is 5 √3 units, then…2025 · asked 3×
- The vector with terminal point A(2,-3,5) and initial point B(3,-4,7) is:2024 · asked 3×
- Find the position vector of point C which divides the line segment joining points A and B having position…2024 · asked 3×
- If a =2 and -3 ≤ k ≤ 2, then k a ∈:2024 · asked 3×
- Unit vector along PQ, where coordinates of P and Q respectively are (2,1,-1) and (4,4,-7), is2023 · asked 3×
CBSE Class 12 Mathematics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.