JAMB Mathematics Past Questions & Answers - Page 330

1,646.

Make 'n' the subject of the formula if w = \(\frac{v(2 + cn)}{1 - cn}\)

A.

\(\frac{1}{c}(\frac{w - 2v}{v + w})\)

B.

\(\frac{1}{c}(\frac{w - 2v}{v - w})\)

C.

\(\frac{1}{c}(\frac{w + 2v}{v - w})\)

D.

\(\frac{1}{c}(\frac{w + 2v}{v + w})\)

Correct answer is A

w = \(\frac{v(2 + cn)}{1 - cn}\)

2v + cnv = w(1 - cn)

2v + cnv = w - cnw

2v - w = -cnv - cnw

Multiply through by negative sign

-2v + w = cnv + cnw

-2v + w = n(cv + cw)

n = \(\frac{-2v + w}{cv + cw}\)

n = \(\frac{1}{c}\frac{-2v + w}{v + w}\)

Re-arrange...

n = \(\frac{1}{c}\frac{w - 2v}{v + w}\)

1,647.

In a class of 46 students, 22 play football and 26 play volleyball. If 3 students play both games, how many play neither?

A.

1

B.

2

C.

3

D.

4

Correct answer is A

n(f \(\cap\) v) + n(f) + n(v) + n(f \(\cap\) v) = 46

3 + 19 + 23 + x = 46

22 + 23 + x = 46

45 + x = 46

x = 46 - 45

x = 1

1,648.

If P is a set of all prime factors of 30 and Q is a set of all factors of 18 less than 10, find P \(\cap\) Q

A.

{3}

B.

{2,3}

C.

{2,3,5}

D.

{1,2}

Correct answer is B

P = {2,3,5}

Q = {2,3,6,9}

P \(\cap\) Q = {2,3}

1,649.

Simplify \((\sqrt{6} + 2)^2 - (\sqrt{6} - 2)^2\)

A.

\(2\sqrt{6}\)

B.

\(4\sqrt{6}\)

C.

\(8\sqrt{6}\)

D.

\(16\sqrt{6}\)

Correct answer is C

\((\sqrt{6} + 2)^2 - (\sqrt{6} - 2)^2\)

= \([(\sqrt{6} + 2) + (\sqrt{6} - 2)][(\sqrt{6} + 2) - (\sqrt{6} - 2)]\)

= \((\sqrt{6} + 2 + \sqrt{6} - 2)(\sqrt{6} + 2 - \sqrt{6} + 2)]\)

= \((2\sqrt{6})(4)\)

= \(8\sqrt{6}\)

1,650.

If log3x2 = -8, what is x?

A.

\(\frac{1}{3}\)

B.

\(\frac{1}{9}\)

C.

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

D.

\(\frac{1}{81}\)

Correct answer is D

log3x2 = -8

x2 = 3-8

x = \(3^{-8 \times \frac{1}{2}}\)

x = 3-4

x = \(\frac{1}{3^4}\)

x = \(\frac{1}{81}\)