2011 - JAMB Mathematics Past Questions and Answers - page 2

11
Find the remainder when X3 - 2X2 + 3X - 3 is divided by X2 + 1
A
2X - 1
B
X + 3
C
2X + 1
D
X - 3
correct option: a

X2 + 1 (\frac{X - 2}{\sqrt{X^3 - 2X^2 + 3n - 3}})

= (\frac {- 6X^3 + n}{-2X^2 + 2X - 3})

= (\frac{(-2X^2 - 2)}{2X - 1})

Remainder is 2X - 1

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12
Factorize completely 9y2 - 16X2
A
(3y - 2x)(3y + 4x)
B
(3y + 4x)(3y + 4x)
C
(3y + 2x)(3y - 4x)
D
(3y - 4x)(3y + 4x)
correct option: d

9y2 - 16x2

= 32y2 - 42x2

= (3y - 4x)(3y +4x)

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13
Solve for x and y respectively in the simultaneous equations -2x - 5y = 3. x + 3y = 0
A
-3, -9
B
9, -3
C
-9,3
D
3, -9
correct option: c

-2x -5y = 3

x + 3y = 0

x = -3y

-2 (-3y) - 5y = -3

6y - 5y = 3

y = 3

but, x = -3y

x = -3(3)

x = -9

therefore, x = -9, y = 3

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14
If x varies directly as square root of y and x = 81 when y = 9, Find x when y = 1\(\frac{7}{9}\)
A
20\(\frac{1}{4}\)
B
27
C
2\(\frac{1}{4}\)
D
36
correct option: d

x (\alpha\sqrt y)

x = k(\sqrt y)

81 = k(\sqrt9)

k = (\frac{81}{3})

= 27

therefore, x = 27(\sqrt y)

y = 1(\frac{7}{9}) = (\frac{16}{9})

x = 27 x (\sqrt{\frac{16}{9}})

= 27 x (\frac{4}{3})

dividing 27 by 3

= 9 x 4

= 36

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15
T varies inversely as the cube of R. When R = 3, T = \(\frac{2}{81}\), find T when R = 2
A
\(\frac{1}{18}\)
B
\(\frac{1}{12}\)
C
\(\frac{1}{24}\)
D
\(\frac{1}{6}\)
correct option: b

T (\alpha \frac{1}{R^3})

T = (\frac{k}{R^3})

k = TR3

= (\frac{2}{81}) x 33

= (\frac{2}{81}) x 27

dividing 81 by 27

k = (\frac{2}{2})

therefore, T = (\frac{2}{3}) x (\frac{1}{R^3})

When R = 2

T = (\frac{2}{3}) x (\frac{1}{2^3}) = (\frac{2}{3}) x (\frac{1}{8})

= (\frac{1}{12})

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16
Solve the inequality -6(x + 3) \(\leq\) 4(x - 2)
A
x \(\leq\) 2
B
x \(\geq\) -1
C
x \(\geq\) -2
D
x \(\leq\) -1
correct option: b

-6(x + 3) (\leq) 4(x - 2)

-6(x +3) (\leq) 4(x - 2)

-6x -18 (\leq) 4x - 8

-18 + 8 (\leq) 4x +6x

-10x (\leq) 10x

10x (\leq) -10

x (\leq) 1

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17
Solve the inequality x2 + 2x > 15.
A
x < -3 or x > 5
B
-5 < x < 3
C
x < 3 or x > 5
D
x > 3 or x < -5
correct option: d

x2 + 2x > 15

x2 + 2x - 15 > 0

(x2 + 5x) - (3x - 15) > 0

x(x + 5) - 3(x + 5) >0

(x - 3)(x + 5) > 0

therefore, x = 3 or -5

then x < -5 or x > 3

i.e. x< 3 or x < -5

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18
Find the sum of the first 18 terms of the series 3, 6, 9,..., 36.
A
505
B
513
C
433
D
635
correct option: b

3, 6, 9,..., 36.

a = 3, d = 3, i = 36, n = 18

Sn = (\frac{n}{2}) [2a + (n - 1)d

S18 = (\frac{18}{2}) [2 x 3 + (18 - 1)3]

= 9[6 + (17 x 3)]

= 9 [6 + 51] = 9(57)

= 513

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19
The seconds term of a geometric series is 4 while the fourth term is 16. Find the sum of the first five terms
A
60
B
62
C
54
D
64
correct option: b

T2 = 4, T4 = 16

Tx = arn-1

T2 = ar2-1 = 4 i.e. ar3 = 16, i.e. ar = 4

T4 = ar4-1

therefore, (\frac{T_4}{T_r}) = (\frac{ar^3}{ar}) = (\frac{16}{4})

r2 = 4 and r = 2

but ar = 4

a = (\frac{4}{r}) = (\frac{4}{2})

a = 2

Sn = (\frac{a(r^n - 1)}{r - 1})

S5 = (\frac{2(2^5 - 1)}{2 - 1})

= (\frac{2(32 - 1)}{2 - 1})

= 2(31)

= 62

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20
A binary operation \(\oplus\) om real numbers is defined by x \(\oplus\) y = xy + x + y for two real numbers x and y. Find the value of 3 \(\oplus\) - \(\frac{2}{3}\).
A
- \(\frac{1}{2}\)
B
\(\frac{1}{3}\)
C
-1
D
2
correct option: b

N + Y = XY + X + Y

3 + -(\frac{2}{3}) = 3(- (\frac{2}{3})) + 3 + (- (\frac{2}{3}))

= -2 + 3 -(\frac{2}{3})

= (\frac{1 - 2}{1 - 3})

= (\frac{1}{3})

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