JAMB Mathematics Past Questions & Answers - Page 371

1,851.

If \(T = 2\pi \sqrt{\frac{l}{g}}\), make g the subject of the formula

A.

(4π l2) / T

B.

(4π2l) / T2

C.

(4π2l2) / T2

D.

(2π√l) / T

Correct answer is B

\(T = 2\pi \sqrt{\frac{l}{g}}\)

\(\frac{T}{2\pi} = \sqrt{\frac{l}{g}}\)

\((\frac{T}{2\pi})^{2} = \frac{l}{g}\)

\(\therefore g = \frac{4 \pi^{2} l}{T^{2}}\)

1,852.

The sum of the first n positive integers is

A.

1/2 n(n-1)

B.

n(n+1)

C.

n(n-1)

D.

1/2 n(n+1)

Correct answer is D

Let the positive integers be 1, 2, ,3, 4, .....n
∴ a = 1, d = 1 and n = n
Sn = n/2(2a + (n-1)d)
= n/2 (2 + n – 1)
= 1/2n(n + 1)

1,853.

The cost of renovating a 6 m square room is N540. What is the cost of renovating a 9 m square room?

A.

N1215

B.

N720

C.

N1620

D.

N810

Correct answer is D

Cost of removing a 6m\(^2\) room = N540
Cost of renovating a 1m\(^2\) room = 540 / 6
Cost of removing a 9m\(^2\) room
= (540 / 6) * 9
= N810

1,854.

Solve the inequalities for which \(\frac{x+4}{3}-\frac{x-3}{2} < 4\)

A.

x < 7

B.

x > -7

C.

x < -7

D.

x > 7

Correct answer is B

\(\frac{x+4}{3}-\frac{x-3}{2} < 4\\
\frac{(2(x+4))-(3(x-3))}{6}<4\)
2(x+4) – 3(x-3) < 4 x 6
2x + 8 – 3x+9 < 24
-x + 17 < 24
-x < 24 – 17
-x < 7
x > -7

1,855.

Find the value of k if the expression kx3 + x2 - 5x - 2 leaves a remainder 2 when it is divided by 2x + 1

A.

10

B.

8

C.

-10

D.

-8

Correct answer is C

F(x) = Q x D + R
Kx3 + x2 - 5x – 2 = Q(2x+1)+R
If 2x+1 = 0 implies x = -1/2
∴k(-1/2)3 + (-1/2)2 -5(-1/2) -2
= Q(2(-1/2) + 1) +2
K(-1/8) + 1/4 + 5/2 - 2 = Q(-1+1)+2
-k/8 + 1/4 + 5/2 - 2 = 0+2
(-k+2+20-16) / 8 = 2
(-k+6) / 8 = 2
-k+6 = 2*8
-k+6 = 16
-k = 16-6
-k = 10
∴k = -10