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WAEC Mathematics Past Questions & Answers - Page 110

546.

A bag contains 4 red and 6 black balls of the same size. If the balls are shuffled briskly and two balls are drawn one after the other without replacement, find the probability of picking balls of different colours

A.

$\frac{8}{15}$

B.

$\frac{13}{25}$

C.

$\frac{11}{15}$

D.

$\frac{13}{15}$

View answer & explanation

Correct answer is A

Prob(RB + BR) = Total balls = 4 + 6 = 10

= prob( $\frac{4}{10} \times \frac{6}{9}$ ) + prob( $\frac{6}{10} \times \frac{4}{9}) = \frac{24}{90} + \frac{24}{90}$

= $\frac{48}{90} = \frac{16}{30} = \frac{8}{15}$

547.

Given that the mean of the scores 15, 21, 17, 26, 18 and 29 is 21, calculate the standard deviation of the scores

A.

$\sqrt{10}$

B.

4

C.

5

D.

$\sqrt{30}$

View answer & explanation

Correct answer is C

$\begin{array}{c|c} x & x - x & (x - \bar{x})^2\\ \hline 15 & -6 & 36\\21 & 0 & 0\\17 & -4 & 16\\ 26 & 5 & 25 \\ 18 & -3 &9 \\ 29 & 8 & 64 \end{array}$

$E(x - \bar{x})^2$ = 150

N = 6

S.D = $\sqrt{\frac{(x - x)^2}{N}}$

S.D = $\sqrt{\frac{150}{6}}$ = 5

548.

A kite flies on a taut string of length 50m inclined at tan angle 54^o to the horizontal ground. The height of the kite above the ground is

A.

50 tan 30^o

B.

50 sin 54^o

C.

50 tan 54^o

D.

50 sin 36^o

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

549.

If cos(x + 40)^o = 0.0872, what is the value of x?

A.

85^o

B.

75^o

C.

65^o

D.

45^o

View answer & explanation

Correct answer is D

cos(x + 40)^o = 0.0872

x + 40 = cos^-10.0872

x + 40^o = 84.99^o

x = 84.99^o - 40^o

x = 44.99

x = 45^o

550.

In $\bigtriangleup$ XYZ, /XY/ = 8cm, /YZ/ = 10cm and /XZ/ = 6cm. Which of these relation is true?

A.

/XY/ + /YZ/ = /XZ/

B.

/XY/ - /YZ/ = /XZ/

C.

/XY/² = /Y/² - /XY/²

D.

/YZ/² = /XZ/² + /XY/²

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

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