2007 - JAMB Mathematics Past Questions and Answers - page 8

71
If the lines 3y = 4x - 1 and qy = x + 3 are parallel to each other, the value of q is
A
-4/3
B
-3/4
C
4/3
D
3/4
correct option: d
If the line 3y = 4x – 1 is parallel t[ line qy = x + 3
Implies gradient of 3y = 4x – 1
Y = 4/3x - 1/3
∴Gradient = 4/3
Gradient of line qy = x + 3
Y = 1/qx + 3/q
∴ Gradient = 1/q
4/3 = 1/q
4q = 3
Q = 3/4
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72
In the parallelogram PQRS above, find angle SQR
A
100o
B
80o
C
50o
D
30o
correct option: a
x = 30o (alternate ∠s b/c PQ//Sr)
Y = 50o (vertical opposite ∠s)
r = 30o (alternate ∠s b/c PQ//SR)
But = y + q + t = 180o (∠s on a straight line)
50 + q + 30 = 180
q + 80 = 180
q = 180 -80
q = 100o
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73
The volume of a hemispherical bowl is \(718\frac{2}{3}\). Find its radius .
A
4.0 cm
B
5.6 cm
C
7.0 cm
D
3.8 cm
correct option: c
Volume of bowl \(\frac{2}{3}\pi r^2\\ 718\frac{2}{3}=\frac{2}{3}\pi r^2\\ \frac{2156}{3}=\frac{2}{3} \times \frac{22}{7} \times r^3
∴r^3 = \frac{2156 \times 3 \times 7}{3 \times 2 \times 22}\\ r^3 = 343\\ r = \sqrt[3]{343}\\ r= 7.0cm\)
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74
A particle P moves between points S and T such that angles SPT is always constant of ST constant. Find the locus off P
A
It is a semi circle with ST as diameter
B
It is a perpendicular bisector of St
C
It is a quadrant of a circle with ST as diameter
D
It is a straight line perpendicular to ST
correct option: a
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75
If the lines 2y - kx + 2 = 0 and y + x - k/2 = 0 Intersect at (1, -2), find the value of k
A
-4
B
-3
C
-2
D
-1
correct option: c
If the point of intersection is (1, -2), it implies that x = 1 and y = -2 when the two equation are solved simultaneously.
∴ substitute x = 1 and y = -2 in any of the equations
2y - k x + 2 = 0
2(-2) - k(1) + 2 = 0
-4 - k + 2 = 0
-4 + 2 = k
-2 = k
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76
A man 40 m from the foot of a tower observes the angle of elevation of the tower to be 30o. Determine the height of the tower.
A
\(\frac{40\sqrt{3}}{3}m\)
B
20 m
C
40√3 m
D
40 m
correct option: a
\(Tan 30 = \frac{h}{40}\\ \frac{1}{\sqrt{3}}=\frac{h}{40}\\ h\sqrt{3}=40\\ h = \frac{40}{\sqrt{3}}\\ h = \frac{40}{\sqrt{3}} \times \frac{\sqrt{3}}{\sqrt{3}}\\ h = \frac{40\sqrt{3}}{3}\)
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77
Find the locus of point equidistant from two straight lines y - 5 = 0 and y - 3 = 0
A
y - 2 = 0
B
y - 4 = 0
C
y - 1 = 0
D
y - 3 = 0
correct option: b
Locus of point P equidistant from y - 5 = 0 and y - 3 = 0 is y = 4 i.e y - 4 = 0
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78
What is the value of k if the mid-point of the line joining (1 - k, - 4) and (2, k + 1) is (-k , k)?
A
-3
B
-1
C
-4
D
-2
correct option: a
(1-k+2) / 2 = - k and -4 + k + 1 = k
3-k = -2k and -3 + k = 2k
K = -3 and k = -3
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79
Find the size of each exterior angle of a regular octagon
A
51o
B
45o
C
40o
D
36o
correct option: b
Each Exterior ∠ = 360/n
= 360/8
= 45o
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80
Find the value of \(\frac{tan 60^o - tan 30^o}{tan 60^o + tan 30^o}\)
A
\(\frac{4}{\sqrt{3}}\)
B
\(\frac{2}{\sqrt{3}}\)
C
1
D
\(\frac{1}{2}\)
correct option: d
\(\frac{tan 60^o - tan 30^o}{tan 60^o + tan 30^o}= \frac{\sqrt{3}-\frac{1}{\sqrt{3}}}{\sqrt{3}+\frac{1}{\sqrt{3}}}\\ =\left(\frac{\sqrt{3}\sqrt{3}-1}{\sqrt{3}}\right)\div \left(\frac{\sqrt{3}\sqrt{3}+1}{\sqrt{3}}\right)\\ =\frac{(3-1)}{(3+1)}\\ =\frac{2}{4}=\frac{1}{2}\)
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