WAEC Past Questions and Answers - Page 1011

5,051.

Given that P = {x : 2 ≤ x ≤ 8} and Q = {x : 4 < x ≤ 12} are subsets of the universal set μ = {x : x ∈ R}, find (P ⋂ Q\(^1\))

A.

{x : 4 < x < 8}

B.

{x : 2 < x ≤ 4}

C.

{x : 2 ≤ x ≤ 4}

D.

{x : 4 ≤ x ≤ 8}

Correct answer is C

Explanation

P = {x : 2 ≤ x ≤ 8} = {2, 3, 4, 5, 6, 7, 8}

Q = {x : 4 < x ≤ 12} = {5, 6, 7, 8, 9, 10, 11, 12}

Q1 = R - {5, 6, 7, 8, 9, 10, 11, 12} = {..., 2, 3, 4, 13, 14, 15, ...}

∴ P ⋂ Q\(^1\) = {2, 3, 4} = {x : 2 ≤ x ≤ 4}

5,052.

Find the fifth term in the binomial expansion of \((q + x)^7\).

A.

\(21q^2x^5\)

B.

\(21q^4x^3\)

C.

\(35q^3x^4\)

D.

\(35q^5x^2\)

Correct answer is C

rth term of a binomial expansion = \(^nC_r - _1a^{n - (r - 1)} b^{r - 1}\)

n = 7, r = 5 ∴ r - 1 = 4

5th term = \(^7C_4 q^{7 - 4} x^4\)

= \(^7C_4 q^3x^4\)

\(\therefore 35q^3x^4\)

5,053.

A particle began to move at \(27 ms^{-1}\) along a straight line with constant retardation of \(9 ms^{-2}\). Calculate the time it took the particle to come to a stop

A.

3 sec

B.

2 sec

C.

4 sec

D.

1 sec

Correct answer is A

\(u = 27 ms^{-1}; a = -9 ms^{-2}; v = 0; t = ?\)

\(v = u + at; t = \frac{v - u}{a}\)

\(t = \frac{0 - 27}{-9} = \frac{-27}{-9}\)

\(\therefore t = 3 sec\)

5,054.

Given that M is the midpoint of T (2, 4) and Q (-8, 6), find the length of MQ .

A.

\(√26 units\)

B.

\(√28 units\)

C.

\(√24 units\)

D.

\(√30 units\)

Correct answer is A

\(|MQ| = \frac{1}{2} |TQ|\)

\(|TQ| = √((y2 - y1)^2 + (x2 - x1)^2)\)

\(|TQ| = √((6 - 4)^2 + (-8 - 2)^2)\)

\(|TQ| = √(2^2 + (-10)^2)\)

\(|TQ| = √(4 + 100) = √104\)

\(|TQ| = 2√26 units\)

\(|MQ| = \frac{1}{2} |TQ| = 2 \times 2√26\)

∴ \(|MQ| = √26 units\)

5,055.

Find the radius of the circle \(2x^2 + 2y^2 - 4x + 5y + 1 = 0\)

A.

\(\frac{\sqrt33}{4}\)

B.

\(\frac{\sqrt5}{6}\)

C.

\(\frac{5}{6}\)

D.

\(\frac{33}{4}\)

Correct answer is A

Standard Form equation of a circle (Center-Radius Form): \((x − a)^2 + (y − b)^2 = r^2\)

Where "a" and "b" are the coordinates of the center and "r" is the radius of the circle

\(2x^2+2y^2-4x+5y+1=0\)

Divide through by 2

= \(x^2+y^2-2x+\frac{5}{2}y+\frac{1}{2}= 0\)

=\(x^2-2x+y^2+\frac{5}{ 2}y=-\frac{1}{ 2}\)

=\(x^2-2x+1^2+y^2+\frac{5}{ 2}y+(\frac{5}{ 4})^2-1-\frac{25}{16}=-\frac{1}{2}\)

=\((x-1)^2+(y+\frac{5}{4})^2=-\frac{1}{2}+1+\frac{25}{16}\)

=\((x-1)^2+(y-(-\frac{5}{4}))^2=\frac{33}{16}\)

=\((x-1)^2+(y-(-\frac{5}{4}))^2=(\frac{\sqrt33}{4})^2\)

\(\therefore a = 1, b = - \frac{5}{4} and\) \(r \frac{\sqrt33}{4} (answer)\)