JAMB Mathematics Past Questions & Answers - Page 172

856.

Evaluate \((2^{0} + 4^{-\frac{1}{2}})^{2}\)

A.

\(\frac{1}{4}\)

B.

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

C.

\(\frac{9}{4}\)

D.

4

E.

9

Correct answer is C

\((2^{0} + 4^{-\frac{1}{2}})^{2}\)

= \((1 + (\frac{1}{4})^{\frac{1}{2}})^{2}\)

= \((1 + \frac{1}{2})^{2}\)

= \((\frac{3}{2})^{2} = \frac{9}{4}\)

857.

Write down the number 0.0052048 correct to three significant figures

A.

0.005

B.

0.0052

C.

0.00520

D.

5.2048

E.

5204

Correct answer is C

0.0052048 = 0.00520

858.

Find, correct to three significant figures, the value of \(\sqrt{41830}\).

A.

205

B.

647

C.

2050

D.

6470

E.

64.7

Correct answer is A

\(\sqrt{41830} = 204.5238\)

\(\approxeq 205\) (to three significant figures)

859.

What is the length of an arc of a circle that substends 2\(\frac{1}{2}\) radians at the centre when the raduis of the circle = \(\frac{k}{k + 1}\) + \(\frac{k + 1}{k}\) then

A.

p< 0

B.

p\(\geq\) 0

C.

p \(\leq\) 0

D.

p < 1

E.

p > 0

Correct answer is E

\(\frac{k}{k + 1}\) + \(\frac{k + 1}{k}\)

= \(\frac{k^2 + (k + 1)^2}{k(k + 10}\)

= \(\frac{2k^2 + 2k + 1}{k(k + 1}\)

let k = \(\frac{1}{2}\)

p = \(\frac{10}{3}\)

p > 0

860.

Solve the given equation \((\log_{3} x)^{2} - 6(\log_{3} x) + 9 = 0\)

A.

27

B.

9

C.

\(\frac{1}{27}\)

D.

18

E.

81

Correct answer is A

\((\log_{3} x)^{2} - 6(\log_{3} x) + 9 = 0\)

Let \(\log_{3} x = a\).

\(a^{2} - 6a + 9 = 0\)

\(a^{2} - 3a - 3a + 9 = 0\)

\(a(a - 3) - 3(a - 3) = 0\)

\((a - 3)(a - 3) = 0\)

\(\implies a = 3 (twice)\)

\(\log_{3} x = 3 \implies x = 3^{3} = 27\)