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WAEC Mathematics Past Questions & Answers - Page 85

421.

Factorize x² + 9x + 20

(x − 5) ²

(x + 5)(x + 4)

(x – 5)(x + 3)

(x + 3) ²

View answer & explanation

Correct answer is B

$x^2 + 9x + 20$

Find the two numbers whose product is 20 and its sum is 9}

$5x \times 4x = 20x^2$

$5x + 4x = 9x$

$(x^2 + 5x) + (4x + 20)$
$x(x + 5)+ 4(x + 5) = (x + 5)(x + 4)$

422.

Simplify 1¼ ÷ (2 ÷ ¼ of 28)

1 $\frac{3}{8}$

2 $\frac{3}{4}$

4 $\frac{3}{8}$

3 $\frac{1}{5}$

View answer & explanation

Correct answer is C

1¼ ÷ [ 2 ÷ ¼] of 28

Apply BODMAS rules

$\frac{5}{4}$ ÷ [ 2 ÷ ¼ × 28 ]

$\frac{5}{4} ÷ \frac{2}{7}$

$\frac{5}{4} × \frac{7}{2}$

$\frac{35}{8}$

= $4 \frac{3}{8}$

423.

In the diagram, O is the centre of the circle of the circle, PR is a tangent to the circle at Q < SOQ = 86^o. Calculate the value of < SQR.

43^o

47^o

54^o

86^o

View answer & explanation

Correct answer is A

Construction: draw a line from Q to point P and another line from S to point P.

< SOQ = 2< QPS (< at centre is twice < on the circumference)

< QPS $\frac{86}{2} = 43$

< SQR = < QPS ( < between a chord and tangent = < in the alternate segment)

< SQR = 43^o

424.

Determine the value of m in the diagram

80^o

90^o

110^o

150^o

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

425.

In the figures, PQ is a tangent to the circle at R and UT is parallel to PQ. if < TRQ = x^o, find < URT in terms of x

2x^o

(90 - x)^o

(90 + x)^o

(180 - 2x)^o

View answer & explanation

Correct answer is D

< URT = < TRQ (angle alternate a tangent and a chord equal to angle in the alternate segment)

< RUT = x^o

In $\bigtriangleup$ URT

< RUT + < RUT + < UTR = 180^o (sum of int. < s of $\bigtriangleup$ )

< URT + x + x = 180^o

< URT = 180^o - 2x