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WAEC Mathematics Past Questions & Answers - Page 83

411.

Given that logx 64 = 3, evaluate x log28

A.

6

B.

9

C.

12

D.

24

Correct answer is C

If logx 64 = 3, then 64=x3

43=x3

Since the indices are equal,

x = 4

Hence, x log2

= 4(3.log22)

= where log22 = 1(1)

= 12 X 1 

= 12

412.

Factorize x22x15

A.

(x + 3)2

B.

(x + 5)(x − 3)

C.

(x − 5)2

D.

(x − 5)(x + 3)

Correct answer is D

x2 − 2x − 15

(x2 − 5x) + (3x − 15)

x(x − 5)+ 3(x − 5)

(x − 5)(x + 3)

413.

Given that A = {1, 5, 7} B = {3, 9, 12, 15} C = {2, 4, 6, 8} Find (A ∪ B) ∪ C

A.

{1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 15}

B.

{1, 2, 3, 5, 6, 8, 12, 15}

C.

{2, 4, 5, 9, 12, 15}

D.

{1, 5, 6, 7, 8, 9, 12, 15}

Correct answer is A

{A ∪ B ∪ C}

{A ∪ B} = {1, 3, 5, 7, 9, 12, 15}

∪ C={2,4,6,8}

{A ∪ B} ∪ C = {1, 3, 5, 7, 9, 12, 15} ∪ {2, 4, 6, 8}

= {1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 15}

{A ∪ B} ∪ C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 15}

414.

Find at which rate per annum simple interest N525 will amount to N588 in 3 years.

A.

3%

B.

2%

C.

5%

D.

4%

Correct answer is D

I = A − P

= N588 − N525

∴I = N63

I = PRT ÷ 100

R = [100I ÷PT]

R = [(100 × 63 ) ÷ (525 × 3)]

= (6300 ÷ 1575) = 4

∴ The rate = 4 %

415.

Make x the subject of the equation
s = 2 + t5(x + ⅗y)

A.

x = 5[(s − 2) ÷ t] - 3/5y

B.

x = 25[(s − 2) ÷ t] − 3ty

C.

x = [1 ÷ (s − 2)3ty]

D.

x = [5(s − 2) 2 ÷ 3ty] × t

Correct answer is A

No explanation has been provided for this answer.