JAMB Mathematics Past Questions & Answers - Page 91

451.

The nth term of the sequence 3, 9, 27, 81.....is

A.

3 x 3n-2

B.

3 x 3n-1

C.

3 x 3n+2

D.

3 x 3n+1

Correct answer is B

3,9,27,81,.....
r = \(\frac{9}{8}\) = 3
Tn = arn-1

Tn = 3(3)n-1 = \(\frac{3(3^2)}{3}\)

452.

If y = 2x3 + 6x2 + 6x + 1, Find \(\frac{dy}{dx}\)

A.

6x2 + 12x + 1

B.

6x2 + 6x + 1

C.

6x2 + 6x + 6

D.

6x2 + 12x + 6

Correct answer is D

y = 2x3 + 6x2 + 6x + 1

\(\frac{dy}{dx}\) = 6x2 + 12x + 6

453.

Evaluate \(\frac{12.02 \times 20.06}{26.04 \times 60.06}\), correct to three significant figures.

A.

0.157

B.

0.154

C.

0.155

D.

0.158

Correct answer is B

\(\frac{12.02 \times 20.06}{26.04 \times 60.06}\) = \(\frac{241.1212}{15698.96}\) = 0.154

454.

The mean of 2-t, 4+t, 3-2t, 2+t and t-1 is

A.

2

B.

t

C.

-t

D.

-2

Correct answer is A

Mean = \(\frac{2 - t + 4 + t + 3 - 2t + 2 + t + t - 1}{5}\)

= \(\frac{10}{5}\) = 2

455.

An arc of the length 16\(\pi\)cm subtends an angle of 80o at the centre of the circle. Find the radius of the circle.

A.

24cm

B.

28cm

C.

36cm

D.

32cm

Correct answer is C

L = \(\frac{\theta}{360}\) x 2\(\pi\)r
16\(\pi\) = \(\frac{80}{360}\) x 2\(\pi\)r

\(\frac{16\pi \times 360}{80 \times 2\pi}\) = r

r = 36cm