WAEC Further Mathematics Past Questions & Answers - Page 130

646.

A body of mass 28g, initially at rest is acted upon by a force, F Newtons. If it attains a velocity of \(5.4ms^{-1}\) in 18 seconds, find the value of F.

A.

0.0082N

B.

0.0084N

C.

0.082N

D.

0.084N

Correct answer is B

\(F = mass \times acceleration\) but \(accl = \frac{v - u}{t}\)

\(\therefore F = m(\frac{v - u}{t})\)

\(Mass = 28g = 0.028kg\)

\(v = 5.4 ms^{-1}; u = 0; t = 18secs\)

\(\therefore F = 0.028(\frac{5.4 - 0}{18}) = 0.028 \times 0.3 = 0.0084N\)

647.

If \(\overrightarrow{OX} = \begin{pmatrix} -7 \\ 6 \end{pmatrix}\) and \(\overrightarrow{OY} = \begin{pmatrix} 16 \\ -11 \end{pmatrix}\), find \(\overrightarrow{YX}\).

A.

\(\begin{pmatrix} 9 \\ -5 \end{pmatrix}\)

B.

\(\begin{pmatrix} -23 \\ -5 \end{pmatrix}\)

C.

\(\begin{pmatrix} 9 \\ 17 \end{pmatrix}\)

D.

\(\begin{pmatrix} -23 \\ 17 \end{pmatrix}\)

Correct answer is D

\(\overrightarrow{OY} \equiv -\overrightarrow{YO}\)

Also, \(\overrightarrow{YO} + \overrightarrow{OX} = \overrightarrow{YX}\)

\(\therefore \overrightarrow{YO} = -\overrightarrow{OY} = - \begin{pmatrix} 16 \\  -11  \end{pmatrix} = \begin{pmatrix} -16 \\ 11  \end{pmatrix}\)

\(\overrightarrow{YX} = \begin{pmatrix}  -16 \\ 11  \end{pmatrix}  + \begin{pmatrix}  -7  \\  6   \end{pmatrix}\)

= \(\begin{pmatrix}  -23  \\  17  \end{pmatrix}\)

648.

What is the probability of obtaining a head and a six when a fair coin and and a die are tossed together? 

A.

\(\frac{1}{12}\)

B.

\(\frac{1}{3}\)

C.

\(\frac{1}{2}\)

D.

\(\frac{2}{3}\)

Correct answer is D

\(\text{p(a head and a six)} = \text{p(a head)} + \text{p(a six)}\)

= \(\frac{1}{2} + \frac{1}{6} = \frac{2}{3}\).

 

 

Hint: Probability of A and B occurring should be greater than probability A or B happening.

649.

Given that \(a = i - 3j\) and \(b = -2i + 5j\) and \(c = 3i - j\), calculate \(|a - b + c|\).

A.

\(\sqrt{13}\)

B.

\(3\sqrt{13}\)

C.

\(6\sqrt{13}\)

D.

\(9\sqrt{13}\)

Correct answer is B

Given \(a = i - 3j; b = -2i + 5j; c = 3i - j\)

\(a- b + c = (1 - (-2) + 3)i + (-3 - 5 + (-1))j = 6i - 9j\)

\(|a - b + c| = \sqrt{6^{2} + (-9)^{2}} = \sqrt{36 + 81} = \sqrt{117}\)

\(= \sqrt{9 \times 13} = 3\sqrt{13}\)

650.

The marks scored by 4 students in Mathematics and Physics are ranked as shown in the table below

Mathematics 3 4 2 1
Physics 4 3 1 2

Calculate the Spearmann's rank correlation coefficient.

A.

0.2

B.

0.5

C.

0.6

D.

0.7

Correct answer is C

Maths (x) Rank \(r_{x}\) Physics (y) Rank \(r_{y}\) \(d = |r_{x} - r_{y}|\) \(d^{2}\)
3 2 4 1 1 1
4 1 3 2 1 1
2 3 1 4 1 1
1 4 2 3 1 1
Total         4

\(\rho = 1 - \frac{6\sum{d^{2}}}{n(n^{2} - 1)}\)

\( 1 - \frac{6 \times 4}{4(4^{2} - 1)} = 1 - \frac{24}{60}\)

= \(1 - 0.4 = 0.6\)