JAMB Mathematics Past Questions & Answers - Page 122

606.

Use the graph of the curve y = f(x)to solve the inequality f(x) \(\leq\) 0

A.

-1 \(\geq\) x \(\geq\) 1, x \(\geq\) 2

B.

x \(\leq\) -1, 1 \(\geq\) x \(\geq\) 2

C.

x \(\geq\) -1, 1 \(\geq\) x \(\geq\) 2

D.

x \(\geq\) 2, -1 \(\geq\) x \(\geq\) 1

Correct answer is B

-1 \(\geq\) x \(\geq\) 1, 1 < x \(\geq\) 2

Combining solutions

= x \(\leq\) 1; 1 \(\geq\) x \(\geq\) 2

608.

The equation of the line in the graph is

A.

3y = 4x + 12

B.

3y = 3x + 12

C.

3y = -4x + 12

D.

3y = -4x + 9

Correct answer is C

Gradient of line = \(\frac{\text{Change in y}}{\text{Change in x}} = \frac{y_2 - y_1}{x_2 - x_1}\)

y2 = 0, y1 = 4

x2 = 3 and x1 = 0

\(\frac{y_2 - y_1}{x_2 - x_1} = \frac{0 - 4}{3 - 0} = \frac{-4}{3}\)

Equation of straight line = y = mx + c

where m = gradient and c = y

intercept = 4

y = 4x + \(\frac{4}{3}\), multiple through by 3

3y = 4x + 12

609.

In the frustum of the cone, the top diagram is twice the bottom diameter. If the height of the frustum is h centimeters, find he height of the cone

A.

2h

B.

2\(\pi\)h

C.

\(\pi\)h

D.

\(\frac{\pi h}{2}\)

Correct answer is A

\(\frac{x}{r}\) = \(\frac{x + h}{2r}\)

2 x r = r (x + h)

Total height of cone = x + h

but x = h

total height = 2h

610.

In the diagram. Find h

A.

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

B.

\(\frac{12}{7} \sqrt{6}\)cm

C.

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

D.

\(\frac{1}{2}\)cm

Correct answer is B

A\(\bigtriangleup\) = \(\sqrt{S(S - a) (S - b)(S - c)}\) (Hero's Formula)

S = \(\frac{a + b + c}{2}\) = \(\frac{5 + 6 + 7}{2}\)

\(\frac{18}{2} = 9\)

A\(\bigtriangleup\) \(\sqrt{9} \times 4 \times 3 \times 2\)

\(\sqrt{216} = 6 \sqrt{6}cm^3\)

A\(\bigtriangleup\) = \(\frac{1}{2} \times 6 \times h\)

6\(\sqrt{6} = \frac{1}{2} \times 7 \times h\)

h = \(\frac{12}{h} \sqrt{6}\)