JAMB Mathematics Past Questions & Answers - Page 193

961.

If w varies inversely as V and U varies directly as w3, Find the relationship between u and v given that u = 1, when v = 2

A.

u = \(\frac{8}{v^3}\)

B.

v = \(\frac{8}{u^2v^3}\)

C.

u = 8v3

D.

v = 8u2

Correct answer is A

W \(\alpha\) \(\frac{1}{v}\)u \(\alpha\) w3

w = \(\frac{k1}{v}\)

u = k2w3

u = k2(\(\frac{k1}{v}\))3

= \(\frac{k_2k_1^2}{v^3}\)

k = k2k1k2

u = \(\frac{k}{v^3}\)

k = uv3

= (1)(2)3

= 8

u = \(\frac{8}{v^3}\)

962.

Simplify log10 a\(\frac{1}{3}\) + \(\frac{1}{4}\)log10 a - \(\frac{1}{12}\)log10a7

A.

1

B.

\(\frac{7}{6}\)log10 a

C.

zero

D.

10

Correct answer is C

log10 a\(\frac{1}{3}\) + \(\frac{1}{4}\)log10 a - \(\frac{1}{12}\)log10a7 = log10 a\(\frac{1}{3}\) + log10\(\frac{1}{4}\) - log10 a\(\frac{7}{12}\)

= log10 a\(\frac{7}{12}\) - log10 a\(\frac{7}{12}\)

= log10 1 = 0

963.

Find x if (x\(_4\))\(^2\) = 100100\(_2\)

A.

6

B.

12

C.

100

D.

210

E.

110

Correct answer is B

x\(_4\) = x \(\times\) 4\(^0\) = x in base 10.

100100\(_2\) = 1 x 2\(^5\) + 1 x 2\(^2\)

= 32 + 4

= 36 in base 10

\(\implies\) x\(^2\) = 36

x = 6 in base 10.

Convert 6 to a number in base 4.

4 6
4 1 r 2
  0 r 1

= 12\(_4\)

964.

The scores of set of final year students in the first semester examination in a paper are 41, 29, 55, 21, 47, 70, 70, 40, 43, 56, 73, 23, 50, 50. Find the median of the scores.

A.

47

B.

50

C.

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

D.

48

E.

49

Correct answer is C

By re-arranging 21, 23, 29, 40, 41, 43| 47, 50| 50, 55, 56, 70, 70, 73

The median = \(\frac{47 + 50}{2}\)

\(\frac{97}{2}\)

= 48\(\frac{1}{2}\)

965.

The lengths of the sides of a right angled triangle are (3x + 1)cm, (3x - 1)cm and xcm. Find x

A.

2

B.

6

C.

18

D.

12

E.

5

Correct answer is D

\((3x + 1)^{2} = (3x - 1)^{2} + x^{2}\) (Pythagoras's theorem)

\(9x^{2} + 6x + 1 = 9x^{2} - 6x + 1 + x^{2}\)

x2 - 12x = 0

x(x - 12) = 0

x = 0 or 12

The sides cannot be 0 hence x = 12.