WAEC Past Questions and Answers - Page 4250

21,246.

Express the product of 0.06 and 0.09 in standard form

A.

5.4 * 10-1

B.

5.4*10-2

C.

5.4*10-3

D.

5.4*102

E.

5.4*103

Correct answer is C

0.06 x 0.09 = 0.0054

= 5.4 x 10-3

21,247.

Evaluate (101.5)2 - (100.5)2

A.

1

B.

2.02

C.

20.02

D.

202

E.

2020

Correct answer is D

(101.5)2 - (100.5)2;(101.5 + 100.5)

202 x 1

= 202

21,248.

If sin\( \theta \) = K find tan\(\theta\), 0° \(\leq\) \(\theta\) \(\leq\) 90°.

A.

1-K

B.

\( \frac{k}{k - 1} \)

C.

\( \frac{k}{\sqrt{1 - k^2}} \)

D.

\( \frac{k}{1 - k} \)

E.

\( \frac{k}{\sqrt{ k^2 - 1}} \)

Correct answer is C

\(\sin \theta = \frac{k}{1}\)

\(\implies 1^2 = k^2 + adj^2\)

\(adj = \sqrt{1 - k^2}\)

\(\therefore \tan \theta = \frac{k}{\sqrt{1 - k^2}}\)

21,249.

If the 2nd and 5th terms of a G.P are 6 and 48 respectively, find the sum of the first for term

A.

-45

B.

-15

C.

15

D.

33

E.

45

Correct answer is E

T\(_{2}\) = ar = 6

T\(_{5}\) = ar\(^{4}\) = 48

\(\frac{T_5}{T_2}\) = \(\frac{ar^{4}}{ar}\) = \(\frac{48}{6}\)

= r\(^{3}\) = 8

⇒ r = 2

S\(_{n}\) = \(\frac{a((r^n) - 1)}{r - 1}\)

S\(_{4}\) = \(\frac{a((r^4) - 1)}{r - 1}\)

S\(_{4}\) = \(\frac{3((2^4) - 1)}{2 - 1}\)

= 3(16 -1)

= 45