JAMB Mathematics Past Questions & Answers - Page 71

351.

An arc of a circle of radius 14cm subtends angle 300° at the centre. Find the perimeter of the sector formed by the arc (take π = \(\frac{22}{7}\))

A.

14.67cm

B.

73.33 cm

C.

101.33cm

D.

513.33cm

Correct answer is C

Length of the arc = \(\frac{\theta}{360} \times 2\pi r\)

= \(\frac{300}{360} \times 2 \times \frac{22}{7} \times 14\)

= \(\frac{220}{3}\)

= 73.33 cm

Perimeter of the sector = Length of the arc + 2r

= 73.33 + 2(14)

= 101.33 cm

352.

The probabilities that John and James pass an examination are \(\frac {3}{4}\)and \(\frac {3}{5}\) respectively. Find the probability of both boys failing the examination.

A.

\(\frac {1}{10}\)

B.

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

C.

\(\frac {9}{20}\)

D.

\(\frac {11}{20}\)

Correct answer is D

Pr(both John and James passed)

  = \(\frac {3}{4}\) x \(\frac {3}{5}\)

  = \(\frac {9}{20}\)

  Pr(john and james failed)= 1- Pr(john and james passed)

  = 1 – \(\frac {9}{20}\)

  = \(\frac {11}{20}\)

  Answer is D

353.

Convert 0.04945 to two significant figures

A.

0.040

B.

0.049

C.

0.050

D.

0.49

Correct answer is B

No explanation has been provided for this answer.

354.

 

If \(\frac{x}{a + 1}\) + \(\frac{y}{b}\) = 1. Make y the subject of the relation.

A.

\(\frac{b(a + 1 - x)}{a + 1}\)

B.

\(\frac{a + 1}{b(a - x + 1)}\)

C.

\(\frac{a(b - x + 1)}{b + 1}\)

D.

\(\frac{b}{a(b - x + 1)}\)

Correct answer is A

No explanation has been provided for this answer.

355.

A school girl spends \(\frac{1}{4}\) of her pocket money on books and \(\frac{1}{3}\) on dress. What fraction remains?

A.

\(\frac{5}{6}\)

B.

\(\frac{7}{12}\)

C.

\(\frac{5}{12}\)

D.

\(\frac{1}{6}\)

Correct answer is C

let the girls' initial pocket money be whole(1)

\(\frac{1}{4}\) of 1 = books, \(\frac{1}{3}\)  of 1 = dress 

fraction of her money left = 1 - \(\frac{1}{4}\) - \(\frac{1}{3}\)

                                   =   \(\frac{5}{12}\)