1998 - JAMB Mathematics Past Questions and Answers - page 5
41
Given that log4(Y - 1) + log4(\(\frac{1}{2}\)x) = 1 and log2(y + 1) + log2x = 2, solve for x and y respectively
A
2, 3
B
3, 2
C
-2, -3
D
-3, -2
correct option: c
log4(y - 1) + log4(\(\frac{1}{2}\)x) = 1
log4(y - 1)(\(\frac{1}{2}\)x) \(\to\) (y - 1)(\(\frac{1}{2}\)x) = 4 ........(1)
log2(y + 1) + log2x = 2
log2(y + 1)x = 2 \(\to\) (y + 1)x = 22 = 4.....(ii)
From equation (ii) x = \(\frac{4}{y + 1}\)........(iii)
put equation (iii) in (i) = y (y - 1)[\(\frac{1}{2}(\frac{4}{y - 1}\))] = 4
= 2y - 2
= 4y + 4
2y = -6
y = -3
x = \(\frac{4}{-3 + 1}\)
= \(\frac{4}{-2}\)
X = 2
therefore x = -2, y = -3
Users' Answers & Commentslog4(y - 1)(\(\frac{1}{2}\)x) \(\to\) (y - 1)(\(\frac{1}{2}\)x) = 4 ........(1)
log2(y + 1) + log2x = 2
log2(y + 1)x = 2 \(\to\) (y + 1)x = 22 = 4.....(ii)
From equation (ii) x = \(\frac{4}{y + 1}\)........(iii)
put equation (iii) in (i) = y (y - 1)[\(\frac{1}{2}(\frac{4}{y - 1}\))] = 4
= 2y - 2
= 4y + 4
2y = -6
y = -3
x = \(\frac{4}{-3 + 1}\)
= \(\frac{4}{-2}\)
X = 2
therefore x = -2, y = -3
42
Find the value of k if \(\frac{k}{\sqrt{3} + \sqrt{2}}\) = k\(\sqrt{3 - 2}\)
A
3
B
2
C
\(\sqrt{3}\)
D
\(\sqrt 2\)
correct option: d
\(\frac{k}{\sqrt{3} + \sqrt{2}}\) = k\(\sqrt{3 - 2}\)
\(\frac{k}{\sqrt{3} + \sqrt{2}}\) x \(\frac{\sqrt{3} - \sqrt{2}}{\sqrt{3} - \sqrt{2}}\)
= k\(\sqrt{3 - 2}\)
= k(\(\sqrt{3} - \sqrt{2}\))
= k\(\sqrt{3 - 2}\)
= k\(\sqrt{3}\) - k\(\sqrt{2}\)
= k\(\sqrt{3 - 2}\)
k2 = \(\sqrt{2}\)
k = \(\frac{2}{\sqrt{2}}\)
= \(\sqrt{2}\)
Users' Answers & Comments\(\frac{k}{\sqrt{3} + \sqrt{2}}\) x \(\frac{\sqrt{3} - \sqrt{2}}{\sqrt{3} - \sqrt{2}}\)
= k\(\sqrt{3 - 2}\)
= k(\(\sqrt{3} - \sqrt{2}\))
= k\(\sqrt{3 - 2}\)
= k\(\sqrt{3}\) - k\(\sqrt{2}\)
= k\(\sqrt{3 - 2}\)
k2 = \(\sqrt{2}\)
k = \(\frac{2}{\sqrt{2}}\)
= \(\sqrt{2}\)
43
A market woman sells oil in cylindrical tins 10cm deep and 6cm in diameter at N15.00 each. If she bought a full cylindrical jug 18cm deep and 10cm in diameter for N50.00, how much did she make by selling all the oil?
A
N62.50
B
N35.00
C
N31.00
D
N25.00
correct option: d
V\(\pi\)r2h = \(\pi\)(3)2(10) = 90\(\pi\)cm3
V = \(\pi\)(5)2 x 18 = 450\(\pi\)cm3
No of volume = \(\frac{450\pi}{90\pi}\)
= 5
selling price = 5 x N15 = N75
profit = N75 - N50 = N25.00
Users' Answers & CommentsV = \(\pi\)(5)2 x 18 = 450\(\pi\)cm3
No of volume = \(\frac{450\pi}{90\pi}\)
= 5
selling price = 5 x N15 = N75
profit = N75 - N50 = N25.00
44
A man is paid r naira per hour for normal work and double rate for overtime. if he does a 35-hour week which includes q hours of overtime, what is his weekly earning in naira?
A
r(35 + q)
B
q(35r - q)
C
q(35 + r)
D
r(35 + 2q)
correct option: d
The cost of normal work = 35r
The cost of overtime = q x 2r = 2qr
The man's total weekly earning = 35r + 2qr
= r(35 + 2q)
Users' Answers & CommentsThe cost of overtime = q x 2r = 2qr
The man's total weekly earning = 35r + 2qr
= r(35 + 2q)
45
When the expression pm2 + qm + 1 is divided by (m - 1), it has a remainder is 4, Find p and q respectively
A
2, -1
B
-1, 2
C
3, -2
D
-2, 3
correct option: b
pm2 + qm + 1 = (m - 1) Q(x) + 2
p(1)2 + q(1) + 1 = 2
p + q + 1 = 2
p + q = 1.....(i)
pm2 + qm + 1 = (m - 1)Q(x) + 4
p(-1)2 + q(-1) + 1 = 4
p - q + 1 = 4
p - q = 3....(ii)
p + q = 1, p - q = -3
2p = -2, p = -1
-1 + q = 1
q = 2
Users' Answers & Commentsp(1)2 + q(1) + 1 = 2
p + q + 1 = 2
p + q = 1.....(i)
pm2 + qm + 1 = (m - 1)Q(x) + 4
p(-1)2 + q(-1) + 1 = 4
p - q + 1 = 4
p - q = 3....(ii)
p + q = 1, p - q = -3
2p = -2, p = -1
-1 + q = 1
q = 2
46
Factorize r2 - r(2p + q) + 2pq
A
(r - 2q)(2r - p)
B
(r - p)(r + p0
C
(r - q)(r - 2p)
D
(2r - q)(r + p)
correct option: c
r2 - r(2p + q) + 2pq = r2 - 2pr -qr + 2pq
= r(r - 2p) - q(r - 2p)
= (r - q)(r - 2p)
Users' Answers & Comments= r(r - 2p) - q(r - 2p)
= (r - q)(r - 2p)
47
Solve for the equation \(\sqrt{x}\) - \(\sqrt{(x - 2)}\) - 1 = 0
A
\(\frac{3}{2}\)
B
\(\frac{2}{3}\)
C
\(\frac{4}{9}\)
D
\(\frac{9}{4}\)
correct option: d
\(\sqrt{x}\) - \(\sqrt{(x - 2)}\) - 1 = 0
= \(\sqrt{x}\) - \(\sqrt{(x - 2)}\) = 1
= (\(\sqrt{x}\) - \(\sqrt{(x - 2)}\))2 = 1
= x - 2 \(\sqrt{x(x - 2)}\) + x -2 = 1
= (2x - 3)2 = [2 \(\sqrt{x(x - 4)}\)]2
= 4x2 - 12x + 9
= 4(x2 - 2x)
= 4x2 - 12x + 9
= 4x2 - 8x
4x = 9
x = \(\frac{9}{4}\)
Users' Answers & Comments= \(\sqrt{x}\) - \(\sqrt{(x - 2)}\) = 1
= (\(\sqrt{x}\) - \(\sqrt{(x - 2)}\))2 = 1
= x - 2 \(\sqrt{x(x - 2)}\) + x -2 = 1
= (2x - 3)2 = [2 \(\sqrt{x(x - 4)}\)]2
= 4x2 - 12x + 9
= 4(x2 - 2x)
= 4x2 - 12x + 9
= 4x2 - 8x
4x = 9
x = \(\frac{9}{4}\)
48
Make \(\frac{a}{x}\) the subject of formula \(\frac{x + 1}{x - a}\)
A
\(\frac{m - 1}{m + 1}\)
B
\(\frac{m + 1}{1 - m}\)
C
\(\frac{m - 1}{1 + m}\)
D
\(\frac{m + 1}{m - 1}\)
correct option: a
\(\frac{x + a}{x - a}\) = m
x + a = mx - ma
a + ma = mx - x
a(m + 1) = x(m - 1)
\(\frac{a}{x}\) = \(\frac{m - 1}{m + a}\)
Users' Answers & Commentsx + a = mx - ma
a + ma = mx - x
a(m + 1) = x(m - 1)
\(\frac{a}{x}\) = \(\frac{m - 1}{m + a}\)