JAMB Mathematics Past Questions & Answers - Page 63

311.

Calculate the area of an equilateral triangle of side 8cm

A.

8√3

B.

16

C.

4√3

D.

16√3

Correct answer is D

An equilateral triangle has all sides equal and all angles equal as 600

  Area = \(\frac{1}{2}\) absinθ

  Area = \(\frac{1}{2}\) x 8 x 8 x sin60

  = \(\frac{1}{2}\) x 64 x \(\sqrt{\frac{3}{2}}\)

  = 16√3 cm\(^2\)

312.

Which one of the following gives the members of the set A1 n B n C?

A.

Φ

B.

{s}

C.

{t, u}

D.

{y, z}

Correct answer is A

A1 = Elements in the universal set but not in A = {s, w, x, y, z} B = {r, s. t, u} C = {t, u, v, w, x} A1 n B n C = elements common to the three sets = none = empty set = Φ

313.

A box contains two red balls and four blue balls. A ball is drawn at random from the box and then replaced before a second ball is drawn. Find the probability of drawing two red balls.

A.

\(\frac{2}{3}\)

B.

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

C.

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

D.

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

Correct answer is D

Total number of balls = 2 + 4 = 6

  P(of picking a red ball) = \(\frac{2}{6}\) = \(\frac{1}{3}\)

  P(of picking a blue ball) = \(\frac{4}{6}\) = \(\frac{2}{3}\)

  With replacement,

  P( picking two red balls) = \(\frac{1}{3}\) × \(\frac{1}{3}\) = \(\frac{1}{9}\)

314.

if y = 23\(_{five}\) + 101\(_{three}\) find y leaving your answer in base two

A.

1110

B.

10111

C.

11101

D.

111100

Correct answer is B

First we convert the numbers to base ten

  23\(_{five}\)= 2 x 51 + 3 x 50

  = 10 + 3 = 13

  101\(_{five}\) = (1 x 32) + (0 x 31) + (1 x 30)

  = 9 + 0 + 1 = 10

  So, y = 13 + 10 = 23

  To convert 23 to base 2 (as in the diagram above)

Y = 23

  = 10111\(_{five}\)

Answer is B

315.

From a point P, Q is 5km due West and R is12km due South of Q. Find the distance between P and R.

A.

5km

B.

12km

C.

13km

D.

17km

Correct answer is C

Using Pythagoras theorem

  PR\(^2\) = 5\(^2\) + 12\(^2\)

  25 + 144 = 169

  PR = √(169)= 13km