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JAMB Mathematics Past Questions & Answers - Page 35

171.

Find the value of x if 2x+2 = 1x2 

A.

32 + 4

B.

32 - 4

C.

3 - 22

D.

4 + 22

Correct answer is A

2x+2 = x - 12

x2 (x - 2) = x + 2 (cross multiply)

x2 - 2 = x + 2 

= x2 - x 

= 2 + 2

x (2 - 1) = 2 + 2

= 2+221×2+12+1

x = 22+2+2+221 

= 32 + 4 

172.

If x is positive real number, find the range of values for which 13x + 12x = 2+3x6x > 14x 

A.

x > -16

B.

x > 0

C.

0 < x < 6

D.

0 < x <16

Correct answer is A

13x + 12x = 2+3x6x > 14x 

= 4(2 + 3x) > 6x = 12x2 - 2x = 0

= 2x(6x - 1) > 0 = x(6x - 1) > 0

Case 1 (-, -) = x < 0, 6x - 1 > 0

= x < 0, x < 16 (solution) 

Case 2 (+, +) = x > 0, 6x - 1 > 0 = x > 0

x > 16

Combining solutions in cases (1) and (2) 

= x > 0, x < 16 = 0 < x < 16 

173.

The pie chart shows the income of a civil servant in month. If his monthly income is N6,000. Find his monthly basic salary. 

A.

N2,050

B.

N2,600

C.

N3,100

D.

N3,450

Correct answer is A

360o - (60o + 60o + 67 + 50 = 237o

360o - 237 = 130o 

B. Salary = 123360XN60001 

= N2,050

174.

Find the simple interest rate percent annum at which N1000 accumulates to N1240 in 3 years. 

A.

6%

B.

8%

C.

10%

D.

12%

Correct answer is B

I = PRT100 = 1 = 1240 - 1000 = 240

R = 240×100100×3 = 8% 

175.

A school boy lying on the ground 30m away from the foot of a water tank towel observes that the angle of elevation of the top of the tank is 60o. Calculate the height of the tank.

A.

603m

B.

303m

C.

203m

D.

103m

Correct answer is B

h = 30 tan 60 

= 303