JAMB Mathematics Past Questions & Answers - Page 29

141.

If w varies inversely as \(\frac{uv}{u + v}\) and w = 8 when

u = 2 and v = 6, find a relationship between u, v, w.

A.

uvw = 16(u + v)

B.

16uv = 3w(u + v)

C.

uvw = 12(u + v)

D.

12uvw = u + v

Correct answer is C

W \(\alpha\) \(\frac{\frac{1}{uv}}{u + v}\)

∴ w = \(\frac{\frac{k}{uv}}{u + v}\)

= \(\frac{k(u + v)}{uv}\)

w = \(\frac{k(u + v)}{uv}\)

w = 8, u = 2 and v = 6

8 = \(\frac{k(2 + 6)}{2(6)}\)

= \(\frac{k(8)}{12}\)

k = 12

i.e 12 ( u + v) = uwv

142.

A car travels from calabar to Enugu, a distance of P km with an average speed of U km per hour and continues to benin, a distance of Q km, with an average speed of Wkm per hour. Find its average speed from Calabar to Benin

A.

\(\frac{(p + q)}{pw + qu}\)

B.

\(\frac{uw(p + q)}{pw + qu}\)

C.

\(\frac{uw(p + q)}{pw}\)

D.

\(\frac{uw}{pw + qu}\)

Correct answer is B

Average speed = \(\frac{total Distance}{Total Time}\)

from Calabar to Enugu in time t1, hence

t1 = \(\frac{P}{U}\)

Also from Enugu to Benin

t2 \(\frac{q}{w}\)

Av. speed = \(\frac{p + q}{t_1 + t_2}\)

= \(\frac{p + q}{p/u + q/w}\)

= p + q x \(\frac{uw}{pw + qu}\)

= \(\frac{uw(p + q)}{pw + qu}\)

143.

Simplify 2log \(\frac{2}{5}\) - log\(\frac{72}{125}\) + log 9

A.

1 - 4 log3

B.

-1 + 2 log 3

C.

-1 + 5 log2

D.

1 - 2log 2

Correct answer is D

2log \(\frac{2}{5}\) - log\(\frac{72}{125}\) + log 9

[\(\frac{2}{5}\))2 x 9] = log \(\frac{4}{25}\) x \(\frac{9}{1}\) x \(\frac{125}{72}\)

= log \(\frac{72}{125}\)

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

= log \(\frac{10}{4}\)

= log 10 - log 4

= log10  - log2\(^2\)

= 1 - 2 log2

144.

Musa borrows N10.00 at 2% per month simple interest and repays N8.00 after 4 months. How much does he still owe?

A.

N10.80

B.

N10.67

C.

N2.80

D.

N2.67

Correct answer is C

I = \(\frac{PRT}{100}\)

= \(\frac{10 \times 2 \times 4}{100}\)

= \(\frac{4}{5}\)

= 0.8

Total amount = N10.80

He pays N8.00

Remainder = 10.80 - 8.00

= N2.80

145.

Find the probability that a number selected at random from 41 to 56 is a multiple of 9

A.

\(\frac{1}{8}\)

B.

\(\frac{2}{15}\)

C.

\(\frac{3}{16}\)

D.

\(\frac{7}{8}\)

Correct answer is A

Given from 41 to 56

41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56

The nos multiple of 9 are: 45, 54

P(multiple of 9) = \(\frac{2}{16}\)

= \(\frac{1}{8}\)