WAEC Past Questions and Answers - Page 3761

18,801.

Given that sin (5x - 28)o = cos (3x - 50)o,0 < x < 90o, find the value of x

A.

14o

B.

21o

C.

32o

D.

39o

Correct answer is B

Sin (5x – 28)o = cos (3x - 50)o
Since by the trigonometry relation
Sin(5x – 28)o = cos[90 – (5x – 28)]o
Hence cos(3x – 50)o = cos[90 – (5x – 28)]o
3x – 50 = 90 - (5x-28)
3x – 50 = 90 – 5x + 28
3x + 5x = 90 + 28 + 50
8x = 168
\(x = \frac{168}{8}=21^{\circ}\)

18,802.

If \(y = 23_{five} + 101_{three}\), find y, leaving your answer in base two

A.

1110

B.

10111

C.

11101

D.

111100

Correct answer is B

\(23_{five} = X_{ten}; X_{ten} = 2\times 5^1 + 3\times 5^0 = 10 + 3 = 13\\
101_{three}=P_{ten}; P_{ten} = 1\times 3^2 + 0\times 3^1 + 1\times 3^0=9+0+1=10_{ten}\\
Y = 13+10=23_{ten}\);
Converting to base two
\(\begin{matrix}
2 & 23\\
2 & 11 &R1\\
2 & 5 & R1\\
2 & 2 & R1\\
2 & 1 & R0\\
& 0& R1 \uparrow\\
\end{matrix} \\
=y=10111_2\)

18,803.

Which of the following statements about water in humans is not correct? it

A.

plays an important role in temperature regulation

B.

acts as solvent for substances conveyed around the body

C.

plays a role in the formation of vitamin

D.

is needed for many life processes

Correct answer is C

No explanation has been provided for this answer.

18,804.

The function of the amniotic fluid in humans is to

A.

protect the foetus against shocks

B.

remove waste products from the foetus

C.

supply food and water to foetus

D.

carry oxygen to the foetus

Correct answer is A

No explanation has been provided for this answer.

18,805.

Placentation of plants is best described as the

A.

arrangement of ovules in the ovary

B.

arrangement of fruits on the branches

C.

development of ovules in the ovary

D.

formation of the pericarp from the ovary wall

Correct answer is A

No explanation has been provided for this answer.