WAEC Mathematics Past Questions & Answers - Page 180

896.

Make f the subject of the relation \(v = u + ft\)

A.

\(\frac{v-u}{t}\)

B.

\(\frac{u-v}{t}\)

C.

\(t(v+u\)

D.

\(\frac{v}{u}-t\)

Correct answer is A

\(v=u+ft \Rightarrow v-u=ft\Rightarrow f=\frac{v-u}{t}\)

897.

Expand (2x-3y)(x-5y)

A.

\(2x^2 + 13xy - 15y^2\)

B.

\(2x^2 - 13xy - 15y^2\)

C.

\(2x^2 + 13xy + 15y^2\)

D.

\(2x^2 - 13xy + 15y^2\)

Correct answer is D

\((2x-3y)(x-5y)=2x^2 - 10xy - 3xy + 15y^2\\
=2x^2 - 13xy + 15y^2\)

898.

Solve the equation \(2^7 = 8^{5-x}\)

A.

\(\frac{5}{8}\)

B.

\(\frac{8}{3}\)

C.

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

D.

\(\frac{15}{4}\)

Correct answer is B

\(2^7 = 2^{3(5-x)}\Rightarrow 7 = 3^{5-x} \Rightarrow 7 15 - 3x\\
\Rightarrow -8 = -3x \Rightarrow x = \frac{8}{3}\)

899.

Convert 101101two to a number in base ten

A.

61

B.

46

C.

45

D.

44

Correct answer is C

1011012 = 1 x 25 + 0 x 24 + 1 x 23 + 1 x 22 + 0 x 21 + 1 x 20 = 32 + 0 + 8 + 4 + 0 + 1 = 4510

900.

In the diagram, PR is a diameter, ∠PRQ = (3x-8)° and ∠RPQ = (2y-7)°. Find x in terms of y

A.

\(x=\frac{75-2y}{3}\)

B.

\(x=\frac{105-3y}{2}\)

C.

\(x=\frac{105-2y}{3}\)

D.

\(x=\frac{75-3y}{2}\)

Correct answer is C

180 = ∠RPQ + ∠PRQ + ∠PQR Since PQR = 90 (theorem: angle in a semi circle)
180 = ∠RPQ + ∠PRQ + 90 => 180° = (3x-8)°+(2y-7)°+90°; 90+8+7 = 3x+2y =>\(\frac{105-2y}{3}=x\)