If (begin{pmatrix} 2 & 1 4 & 3 end{pmatrix})(begin{pmatrix} 5 4 end{pmatrix}) = k(begin{pmatrix} 17.5

FURTHER MATHEMATICSWAEC 2017

If \(\begin{pmatrix} 2 & 1 \\ 4 & 3 \end{pmatrix}\)\(\begin{pmatrix} 5 \\ 4 \end{pmatrix}\) = k\(\begin{pmatrix} 17.5 \\ 40.0 \end{pmatrix}\), find the value of k.

  • A. 1.2
  • B. 3.6
  • C. 0.8
  • D. 0.5

Correct Answer: C. 0.8

Explanation

\(\begin{pmatrix} 2 & 1 \\ 4 & 3 \end{pmatrix}\)\(\begin{pmatrix} 5 \\ 4 \end{pmatrix}\) = k\(\begin{pmatrix} 17.5 \\ 40.0 \end{pmatrix}\)

\(\begin{pmatrix} 10 + 4 \\ 20 + 12\end{pmatrix}\) = \(\begin{pmatrix} 14 \\ 32\end{pmatrix}\) = k\(\begin{pmatrix} 17.5 \\ 40.0 \end{pmatrix}\)

k = \(\frac{14}{17.5} = \frac{32}{40} = 0.8\)

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