2007 - WAEC Mathematics Past Questions and Answers - page 3

21
If p αIQ which of the following is true?
A
q αp2
B
q α1p2
C
q αp
D
q α1p
correct option: d

p (\alpha \frac{I}{Q}); p (\frac{k}{q}) (where k is constant)

q = (\frac{k}{p})

q (\alpha \frac{1}{p})

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22
Simplify 3451215+1620, leaving your answer in surd form
A
295
B
1415
C
1215
D
1115
correct option: a

3 (\sqrt{45} - 12\sqrt{5} + 16\sqrt{20})

= 3 x (\sqrt{9 \times 5} - 12 \times \sqrt{5} + 16 \times \sqrt{4 \times 5})

= 3 x 3 x (\sqrt{5} - 12 \times \sqrt{5} + 16 \times 2 \times \sqrt{5})

= 9(\sqrt{5} - 2 \sqrt{5} + 32 \sqrt{5})

= 9(\sqrt{5} + 32\sqrt{5} - 12\sqrt{5})

= 29(\sqrt{5})

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23
Which of the following statement is true for the ste P = {-3.2 x < 5} where x is an integer?
A
least value of x is -3.2
B
least value of x is -3
C
greatest value of x is 4.9
D
greatest value of x is 5
correct option: b

p = {-3.2.....4.9}; Since x is an integer

least value of x is -3

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24
Simplify 3x3(3x)3
A
1
B
13
C
19
D
127
correct option: c

(\frac{3x^3}{(3x)^3}) = (\frac{3 \times x^3}{3^3 \times x^3})

= (\frac{3 \times x^3}{3 \times 3 \times 3 \times x^3})

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

= (\frac{1}{9})

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25
N140,000 is shared between Abu, Kayode and Uche. Abu has twice as much as Kayode and Kayode has twice as much as Uche. What is Kayode'sshare?
A
N80,000
B
N40,000
C
N2,000
D
10,000
correct option: b

Let Abu's share = 2x;

Kayode's = x

Uche's share = (\frac{x}{2})

Total: 2x + x + (\frac{x}{2}) = N140,000

(\frac{7x}{2}) = N140,000

x = (\frac{280,000}{7}) = N40,000

Kayode's share = N40,000

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26
I am x years old and my brother is 3 years older. How old was my brother last year?
A
(x - 4)years
B
(x + 2) years
C
(3x - 10years
D
(3x + 1)years
correct option: b

I am x years old; My brother = 3 + x; My brother

last year = (3 + x) - 1 = x + 3 - 1

= (x + 2) years

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27
For what value of x is the expression 2x1x+3 not defined?
A
3
B
2
C
12
D
-3
correct option: d

(\frac{2x - 1}{x + 3}) not defined

x + 3 = 0

x = -3

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28
If x = 3, Y = 2 and z = 4, what is the value of 3x2 - 2y + z?
A
17
B
27
C
35
D
71
correct option: b

x = 3, y = 2, z = 4

3x2 - 2y + z

= 3(3)2 - 2(2) + 4

3(9) - 4 + 4 = 27

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29
Solve the simultaneous equations x + y = 2 and 3x - 2y = 1
A
x = 2 and y = 1
B
x = 1 and y = 1
C
x = 1 and y = 2
D
x = -1 and y = 1
correct option: b

x + y = 2........... (i)

3x - 2y = 1......(ii)

From (i): x = 2 - y ..........(iii)

subt. (2 - y) for x in (ii)

3(2 - y) 2y = 1

6 - 3y - 2y = 1

-5y = 1 - 6 = -5

y = (\frac{-5}{-5}) = 1

subst. (i) for y in (iii)

x = 2 - 1 = 1

x = 1, y = 1

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30
If 8x-1 = 14, find x
A
-53
B
-1
C
-13
D
13
correct option: d

8x-1 = (\frac{1}{4})

23(x - 1 = 2-2

3x - 3 = -2

3x = -2 + 3

3x = 1

x = (\frac{1}{3})

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