JAMB Mathematics Past Questions & Answers - Page 161

801.

Simplify 2\(\frac{5}{12}\) - 1\(\frac{7}{8}\) x \(\frac{6}{5}\)

A.

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

B.

\(\frac{13}{20}\)

C.

\(\frac{11}{30}\)

D.

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

E.

\(\frac{5}{3}\)

Correct answer is A

2\(\frac{5}{12}\) - 1\(\frac{7}{8}\) x \(\frac{6}{5}\) = \(\frac{29}{12}\) - \(\frac{15}{8}\) x \(\frac{6}{5}\)

= \(\frac{29}{12}\) - \(\frac{9}{4}\)

= \(\frac{29 - 27}{12}\)

= \(\frac{2}{12}\)

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

802.

A ladder resting on a vertical wall makes an angles whose tangent is 2.4 with the ground. If the distance between the foot of the ladder and the wall is 50cm, What is the length of the ladder?

A.

1m

B.

1.1m

C.

1.2m

D.

0.9m

E.

1.3m

Correct answer is E

If tan\(\theta\) = 2, 4

\(\theta\) = tan-1(2.4)

= 67o 25

By sin formula \(\frac{x}{sin 90^o}\) = \(\frac{50}{sin 22^o 37}\)

= \(\frac{50}{sin(9o - \theta)}\)

sin90o = 1

x = 50 cosec 22o 37

= 50 x 2.604x

= 130cm

but 100cm = 1m

130cm = 1.3m

803.

Simplify \(\frac{x^2 + y^2 + xy}{x + y}\) - \(\frac{x^2 + y^2}{x - y}\)

A.

\(\frac{x^2 + y^2} {(x - y)^2}\)

B.

\(\frac{2y^3} {y^2 - x^2}\)

C.

\(\frac{3x^2 + y^2} {(2x - y)^2}\)

D.

\(\frac{x^2 + y^2} {(x^2 - y)}\)

Correct answer is B

\(\frac{x^2 + y^2 + xy}{x + y}\) - \(\frac{x^2 + y^2}{x -y}\)

= \(\frac{-y^3 - y^3}{x^2 - y^2}\)

= \(\frac{2y^3}{x^2 - y^2}\)

= \(\frac{2y^3}{y^2 - x^2}\)

804.

A steel ball of radius 1 cm is dropped into a cylinder of radius 2cm and height 4cm. If the cylinder is now filled with water, what is the volume of the water in the cylinder?

A.

\(\frac{44}{3}\)\(\pi\)cm3

B.

12\(\pi\)cm3

C.

\(\frac{38}{3}\)\(\pi\)cm3

D.

\(\frac{40}{3}\)\(\pi\)cm3

E.

\(\frac{32}{33}\)\(\pi\)cm3

Correct answer is A

Volume of steel ball = \(\frac{4\pi r^2}{3}\)

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

= \(\frac{4 \pi}{3}\)cm3

Vol. of cylinder = \(\pi\)r2h

= \(\pi\) x 22 x 3

Vol. of water = 16\(\pi\) - \(\frac{4 \pi}{3}\)

= \(\frac{48 - 4 \pi}{3}\)

= \(\frac{44 \pi}{3}\)cm3

805.

Simplify \(\frac{5^x \times 25^{x - 1}}{125^{x + 1}}\)

A.

52x + 1

B.

5x + 1

C.

5-5

D.

52

E.

53

Correct answer is C

\(\frac{5^x \times 25^{x - 1}}{125^{x + 1}}\) = \(\frac{5^x \times 5^{2x - 2}}{5^{3x + 3}}\)

= \(\frac{5^{x + 2x - 2}}{5^{3x + 3}}\)

= \(\frac{5^{3x - 2}}{5^{3x + 3}}\)

= 5\(^{3x - 2 - 3x - 3}\)

= 5\(^{-5}\)