WAEC Further Mathematics Past Questions & Answers - Page 22

106.

If 2y\(^2\) + 7 = 3y - xy, find \(\frac{dy}{dx}\)

A.

\(\frac{-y}{4x+y-3}\)

B.

\(\frac{y}{4x+y-3}\)

C.

\(\frac{-y}{4x+x-3}\)

D.

\(\frac{y}{4x+x-3}\)

Correct answer is D

2y\(^2\) + 7 = 3y - xy, find \(\frac{dy}{dx}\)

4y  \(\frac{dy}{dx}\) + 0 = 3 \(\frac{dy}{dx}\) - x  \(\frac{dy}{dx}\) + y

{4x+x-3}  \(\frac{dy}{dx}\) = y

= \(\frac{y}{4x+x-3}\)

107.

A fair die is tossed 60 times and the results are recorded in the table

Number of die 1 2 3 4 5 6
Frequency 15 10 14 2 8 11

Find the probability of obtaining a prime number.

A.

\(\frac{7}{30}\)

B.

\(\frac{1}{6}\)

C.

\(\frac{7}{15}\)

D.

\(\frac{8}{15}\)

Correct answer is D

Prime number in the experiment are 2,3 and 5 with frequencies 10,14 and 8

P(obtaining a prime number) = \(\frac{10+14+8}{60}\)

= \(\frac{32}{60}\) or \(\frac{8}{15}\)

108.

A body of mass 15kg is placed on a smooth plane which is inclined at 60° to the horizontal. If the box is at rest,

calculate the normal reaction to the plane. [ Take g = 10m/s\(^2\) ]

A.

129.9N

B.

75N

C.

60.0N

D.

7.5N

Correct answer is B

Let  the normal reaction be R

R = Wcosø = mgcosø

= 15 * 10cos 60°

= 150 * 0.5000

= 75N

109.
110.

Find the inverse of  \(\begin{pmatrix} 4 & 2 \\ -3 & -2 \end{pmatrix}\)

A.

\(\begin{pmatrix} 1 & 1 \\ -1.5 & -2 \end{pmatrix}\)

B.

\(\begin{pmatrix} 1 & -1 \\ 1.5 & -2 \end{pmatrix}\)

C.

\(\begin{pmatrix} -2 & 1 \\ 1.5 & 1 \end{pmatrix}\)

D.

\(\begin{pmatrix} -2 & -1 \\ 1.5 & 1 \end{pmatrix}\)

Correct answer is A

Let A =  \(\begin{pmatrix} 4 & 2 \\ -3 & -2 \end{pmatrix}\);

|A| = -8 - (-6) = -8 + 6

|A| = -2

A\(^{-1}\) = \(\frac{1}{-2}\) =  \(\begin{pmatrix} -2 & 2- \\ 3 & 4 \end{pmatrix}\)

= \(\begin{pmatrix} 1 & 1 \\ -1.5 & -2 \end{pmatrix}\)