1.

If \(\vec{a}\)=9\(\hat{i}\)-2\(\hat{j}\)+7\(\hat{k}\), \(\vec{b}\)=5\(\hat{i}\)+\(\hat{j}\)-3\(\hat{k}\), find \(\vec{a}+\vec{b}\).(a) \(\hat{i}\)–\(\hat{j}\)+4\(\hat{k}\)(b) 14\(\hat{i}\)–\(\hat{j}\)+4\(\hat{k}\)(c) 14\(\hat{i}\)-3\(\hat{j}\)+4\(\hat{k}\)(d) 14\(\hat{i}\)–\(\hat{j}\)+9\(\hat{k}\)I had been asked this question in final exam.This intriguing question comes from Addition of Vectors in division Vector Algebra of Mathematics – Class 12

Answer»

The CORRECT choice is (b) 14\(\hat{i}\)–\(\hat{j}\)+4\(\hat{k}\)

The best I can EXPLAIN: Given that, \(\vec{a}\)=9\(\hat{i}\)-2\(\hat{j}\)+7\(\hat{k}\), \(\vec{b}\)=5\(\hat{i}\)+\(\hat{j}\)-3\(\hat{k}\)

We have to find \(\vec{a}+\vec{b}\)

∴\(\vec{a}+\vec{b}\)=(9\(\hat{i}\)-2\(\hat{j}\)+7\(\hat{k}\))+(5\(\hat{i}\)+\(\hat{j}\)-3\(\hat{k}\))

=(9+5) \(\hat{i}\)+(-2+1) \(\hat{j}\)+(7-3)\(\hat{k}\)

=14\(\hat{i}\)–\(\hat{j}\)+4\(\hat{k}\)



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