1.

Find vector \(\vec{c}\), if \(\vec{a}\)–\(\vec{b}\)+\(\vec{c}\)=6\(\hat{i}\)+8\(\hat{j}\) where \(\vec{a}\)=7\(\hat{i}\)+2\(\hat{j}\) and \(\vec{b}\)=4\(\hat{i}\)-5\(\hat{j}\).(a) -3\(\hat{i}\)+\(\hat{j}\)(b) 3\(\hat{i}\)+\(\hat{j}\)(c) 3\(\hat{i}\)–\(\hat{j}\)(d) -3\(\hat{i}\)–\(\hat{j}\)The question was asked during an online interview.This interesting question is from Addition of Vectors in division Vector Algebra of Mathematics – Class 12

Answer»

The correct option is (b) 3\(\hat{i}\)+\(\hat{j}\)

The explanation: Given that, \(\VEC{a}\)–\(\vec{b}\)+\(\vec{c}\)=6\(\hat{i}\)+8\(\hat{j}\) -(1)

It is also given that, \(\vec{a}\)=7\(\hat{i}\)+2\(\hat{j}\) and \(\vec{b}\)=4\(\hat{i}\)-5\(\hat{j}\)

Substituting the values of \(\vec{a}\) and \(\vec{b}\) in equation (1), we get

\(\vec{a}\)–\(\vec{b}\)+\(\vec{c}\)=6\(\hat{i}\)+8\(\hat{j}\)

(7\(\hat{i}\)+2\(\hat{j}\))-(4\(\hat{i}\)-5\(\hat{j}\))+\(\vec{c}\)=6\(\hat{i}\)+8\(\hat{j}\)

∴\(\vec{c}\)=(6\(\hat{i}\)+8\(\hat{j}\))-(7\(\hat{i}\)+2\(\hat{j}\))+(4\(\hat{i}\)-5\(\hat{j}\))

=(6-7+4) \(\hat{i}\)+(8-2-5) \(\hat{j}\)

=3\(\hat{i}\)+\(\hat{j}\)



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