10 questions from the JAMB 2012 Mathematics paper, with answers and explanations. Tap "Show answer" under each one when you are ready.
JAMB 2012Question 1 · Algebraic Processes
Make 'n' the subject of the formula if w = 1−cnv(2+cn)
A.c1(v+ww−2v)
B.c1(v−ww−2v)
C.c1(v−ww+2v)
D.c1(v+ww+2v)
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Answer: A.c1(v+ww−2v)
n = (1/c)(w-2v)/(v+w) after cross-multiplying and collecting terms.
JAMB 2012Question 2 · Algebraic Processes
Given that I3 is a unit matrix of order 3, find ∣I3∣
A.-1
B.0
C.1
D.2
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Answer: C. 1
The determinant of any identity matrix is 1.
JAMB 2012Question 3 · Coordinate Geometry and Trigonometry
The gradient of the straight line joining the points P(5, -7) and Q(-2, -3) is
A.21
B.52
C.-74
D.-32
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Answer: C. -74
Gradient = (-3+7)/(-2-5) = 4/-7 = -4/7.
JAMB 2012Question 4 · Coordinate Geometry and Trigonometry
A man stands on a tree 150cm high and sees a boat at an angle of depression of 74∘. Find the distance of the boat from the base of the tree.
A.52cm
B.43cm
C.40cm
D.15cm
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Answer: B.43cm
Distance = 150/tan74° ≈ 43.
JAMB 2012Question 5 · Inequalities, Permutation, and Combination
The value of y for which 51y + 51 < 21y + 52 is
A.y > 32
B.y < 32
C.y > -32
D.y < -32
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Answer: C. y > -32
Multiplying through by 10 and simplifying gives y > -2/3.
JAMB 2012Question 6 · Number, Fractions, and Approximation
Convert (112)6 to base three.
A.(2211)3
B.(2121)3
C.(1212)3
D.(1122)3
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Answer: D.(1122)3
(112)6=4410, and 4410=(1122)3.
JAMB 2012Question 7 · Number, Fractions, and Approximation
A man earns N3,500 per month out of which he spends 15% on his children's education. If he spends additional N1,950 on food, how much does he have left?
A.N525
B.N1,025
C.N1,950
D.N2,975
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Answer: B. N1,025
3500 - 525 (15%) = 2975; 2975 - 1950 = 1025.
JAMB 2012Question 8 · Sequences, Series, and Variation
If y varies directly as n and y = 4 when n = 4, find y when n = 197
A.17
B.34
C.38
D.32
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Answer: C.38
y=2n; at n=916, y=2×34=8/3.
JAMB 2012Question 9 · Sets and Binary Operations
If P is a set of all prime factors of 30 and Q is a set of all factors of 18 less than 10, find P∩Q
A.{3}
B.{2,3}
C.{2,3,5}
D.{1,2}
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Answer: B. {2,3}
Prime factors of 30 = {2,3,5}; factors of 18 <10 = {1,2,3,6,9}; intersection = {2,3}.
JAMB 2012Question 10 · Statistics and Probability
The mean of seven numbers is 96. If an eighth number is added, the mean becomes 112. Find the eighth number.
A.126
B.180
C.216
D.224
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Answer: D. 224
Sum of 8 numbers - sum of 7 numbers = 896-672 = 224.
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