JAMB Mathematics Past Questions & Answers - Page 80

396.

Given m = N\(\sqrt{\frac{SL}{T}}\) make T the subject of the formula

A.

\(\frac{\text{NSL}}{M}\)

B.

\(\frac{N^2SL}{M^2}\)

C.

\(\frac{N^2SL}{M}\)

D.

\(\frac{NSL}{M^2}\)

Correct answer is B

M = N \(\sqrt{\frac{SL}{T}}\),

make T subject of formula square both sides

M\(^{2}\) = \(\frac{N^2SL}{T}\)

TM\(^{2}\) = N\(^{2}\)SL

T = \(\frac{N^2SL}{M^2}\)

397.

Evaluate 1 - (\(\frac{1}{5}\) x \(\frac{2}{3}\)) + ( 5 + \(\frac{2}{3}\))

A.

4

B.

3

C.

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

D.

\(\frac{98}{15}\)

Correct answer is D

No explanation has been provided for this answer.

398.

If temperature t is directly proportional to heat h, and when t = 20oC, h = 50 J, find t when h = 60J

A.

24oC

B.

20oC

C.

34oC

D.

30oC

Correct answer is A

t ∝ h, t = 20, h

t = ? h = 60

t = kh where k is constant

20 = 50k

k = \(\frac{20}{50}\)

k = \(\frac{2}{5}\)

when h = 60, t = ?

t = \(\frac{2}{5}\) × 60

t = 24oC

399.

If y = x Sin x, find \(\frac{dy}{dx}\) when x = \(\frac{\pi}{2}\)

A.

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

B.

-1

C.

1

D.

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

Correct answer is C

y = xsinx

\(\frac{dy}{dx}\) = \(1 \sin x + x \cos x\)

= \(\sin x + x \cos x\)

At x = \(\frac{\pi}{2}\)

= sin\(\frac{\pi}{2}\) + \(\frac{\pi}{2} \cos {\frac{\pi}{2}}\)

= 1 + \(\frac{\pi}{2}\) × 0

= 1

400.

Evaluate (\(\sin\)45º + \(\sin\)30º ) in surd form

A.

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

B.

√3 − \(\frac{1}{2}\)

C.

\(\frac{1}{2}\)√2

D.

1 + \(\frac{\sqrt{2}}{2}\)

Correct answer is D

hypotenuse
sin = \(\frac{1}{2}\)

\(\sin45 = \frac{1}{\sqrt{2}}\)

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

∴ (sin45 + sin30)

= \(\frac{1}{\sqrt{2}} + \frac{1}{2}\)

= \(\frac{\sqrt{2}}{2}\) + \(\frac{1}{2}\)

= \(\frac{\sqrt{2} + 1}{2}\)

= \(\frac{1 + \sqrt{2}}{2}\)