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Provide solution for RD Sharma maths class 12 chapter 22 Algebra of Vectors exercise Multiple choice question 27

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Answer:\sqrt{209}

Hint: |\vec{a}+\vec{b}+\vec{c}|

Given: If  \vec{a}, \vec{b}, \vec{c}  are position vectors of point A(2,3,-4), B(3,-4,-5) \; \& \; C(3,2,-3)

Then |\vec{a}+\vec{b}+\vec{c}| is equal to

Solution:

            \begin{aligned} &\vec{a}=2 \hat{i}+3 \hat{j}-4 \hat{k} \\\\ &\vec{b}=3 \hat{i}-4 \hat{j}-5 \hat{k} \\\\ &\vec{c}=3 \hat{i}+2 \hat{j}-3 \hat{k} \end{aligned}

            \begin{gathered} |\vec{a}+\vec{b}+\vec{c}|=(2+3+3) \hat{i}+(3-4+2) \hat{j}+(-4-5-3) \hat{k} \\\\ \end{gathered}

                                =8 \hat{i}+\hat{j}-12 \hat{k}

            Magnitude:

                            \begin{aligned} &=\sqrt{8^{2}+1^{2}+(-12)^{2}} \\\\ &=\sqrt{64+1+144} \\\\ &=\sqrt{209} \end{aligned}

 

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