Vector Algebra
NCERT Exemplar Class 12
CBSE
Grade 12
Question:
If $\vec{a} = 3\hat{i} - \hat{j} + 4\hat{k}$ and $\vec{b} = 2\hat{i} + 4\hat{j} - 3\hat{k}$, then $|\vec{a} + \vec{b}|$ is:
(a) $\sqrt{35}$
(b) $\sqrt{34}$
(c) $5$
(d) $6$
Step-by-Step Solution
a + b = 5\hat{i} + 3\hat{j} + \hat{k} \implies |a+b| = \sqrt{25+9+1} = \sqrt{35}. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Selecting $\sqrt{35}$: 1.0 Mark
Correct Answer: $\sqrt{35}$
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