JAMB Mathematics Past Questions & Answers - Page 158

786.

The solution of the equation x2 - 2x = 8 is

A.

x = 0 or 2

B.

x = -2 or 4

C.

x = 2

D.

x = -4

E.

x = 2 or 4

Correct answer is B

x2 - 2x = 8 = 8

x2 - 2x - 8 = 0

(x2 - 4x) + (2x - 8) = 0

When x + 2 = 0

x = -2, when x - 4 = 0

x = 4

-2 or 4

787.

x is directly proportional to y and inversely proportional to z. If x = 9 when y = 24 and z = 8, what is the value of x when y = 5 and z = 6?

A.

\(\frac{5}{6}\)

B.

11

C.

3\(\frac{3}{5}\)

D.

2\(\frac{1}{2}\)

E.

1\(\frac{1}{5}\)

Correct answer is D

x \(\alpha\) y = x \(\alpha\) \(\frac{1}{z}\)

x \(\alpha\) \(\frac{1}{z}\)

x = k \(\frac{y}{z}\)

k = \(\frac{xz}{y}\) = \(\frac{9 \times 8}{24}\)

= 3

x = \(\frac{xz}{y}\)

= \(\frac{3 \times 5}{6}\)

= \(\frac{15}{6}\)

= \(\frac{5}{2}\)

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

788.

The annul profits of a transport business were divided between the partners A and B in the ratio 3 : 5. If B received N3000 more than A, the total profit was

A.

N5000

B.

N1800

C.

N12000

D.

N24000

E.

N8000

Correct answer is C

A : B = 3 : 5

Total ratio = 3 + 5 = 8

Let rept, the total profit, A receives \(\frac{3x}{8}\)

\(\frac{5x}{8}\) - \(\frac{3}{x}\) = 3000

\(\frac{5x}{8}\) - \(\frac{3x}{8}\) = 3000

= \(\frac{2x}{8}\)

= 3000

2x = 2400

x = 1200

N12,000

789.

In base ten, the number 101101 (base 2) equals

A.

15

B.

4

C.

45

D.

32

E.

90

Correct answer is C

(101101)2 \(\begin{array}{c|c} 2^5 & 2^4 & 2^3 & 2^2 & 2^1 & 2^o\\ \hline 1 & 0 & 1 & 1 & 0 & 1\end{array}\)

= 1 x 25 + 0 x 24 + 1 x 23 + 1 x 22 + 0 x 21 + 1 x 2o

= 32 + 0 + 8 + 4 + 0 + 1

= (45)10

790.

After getting a rise of 15%, a man's new monthly salary is N345. How much per month did he earn before the increase?

A.

N330

B.

N396.75

C.

N300

D.

N293.25

E.

N360

Correct answer is C

Let x represent his monthly salary before increase 15% of

x = 345

% profit = (100 + 15)%

= 115%

\(\frac{115}{100}\)x = 345

115x = 34500

x = N300.00