Question 56:

• WAEC 2017

There are 7 boys in a class of 20. Find the number of ways of selecting 3 girls and 2 boys

A. 1638
B. 2730
C. 6006
D. 7520

Question 57:

• WAEC 2017

The 3rd and 7th term of a Geometric Progression (GP) are 81 and 16. Find the 5th term.

A. \(\frac{4}{729}\)
B. \(\frac{81}{16}\)
C. 27
D. 36

Question 58:

• WAEC 2017

If \(B = \begin{pmatrix} 2 & 5 \\ 1 & 3 \end{pmatrix}\), find \(B^{-1}\).

A. \(A = \begin{pmatrix} -3 & -5 \\ 1 & 2 \end{pmatrix}\)
B. \(A = \begin{pmatrix} 3 & -5 \\ 1 & 2 \end{pmatrix}\)
C. \(A = \begin{pmatrix} 3 & -5 \\ -1 & 2 \end{pmatrix}\)
D. \(A = \begin{pmatrix} -3 & 5 \\ 1 & -2 \end{pmatrix}\)

Question 59:

• WAEC 2017

\(\alpha\) and \(\beta\) are the roots of the equation \(2x^{2} - 3x + 4 = 0\). Find \(\frac{\alpha}{\beta} + \frac{\beta}{\alpha}\)

A. \(\frac{-9}{8}\)
B. \(\frac{-7}{8}\)
C. \(\frac{7}{8}\)
D. \(\frac{9}{8}\)

Question 60:

• WAEC 2017

Given that \(\sin x = \frac{5}{13}\) and \(\sin y = \frac{8}{17}\), where x and y are acute, find \(\cos(x+y)\).

A. \(\frac{130}{221}\)
B. \(\frac{140}{221}\)
C. \(\frac{140}{204}\)
D. \(\frac{220}{23}\)