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WAEC Mathematics Past Questions & Answers - Page 91

451.

A box contains 13 currency notes, all of which are either N50 or N20 notes. The total value of the currency notes is N530. How many N50 notes are in the box?

View answer & explanation

Correct answer is D

let the number of N50 notes = x let the number of N20 notes = y from the first statement x + y = 13.....(1) from the second statement 50x + 20y = 530 ......(2) dividing through by 10, we have 5x + 2y = 53 ....(20 solving simultaneously by eliminating x + y = 12....(1) 5x + 2y = 53.....(2) multiply eqn (1) by 2 multiply eqn (2) by 1 2x + 2y = 26 -5x + 2y = 53 -3x = -27 x = 9 substitute x = 9 into equation (1) x + y = 13 y = 13 - x = 13 - 9 = 4 y = 4 the number of N50 notes = 9

452.

A ship sails x km due east to a point E and continues x km due north to F. Find the bearing the bearing of f from the starting point.

045^o

090^o

135^o

225^o

View answer & explanation

Correct answer is A

No explanation has been provided for this answer.

453.

Which of the following is a measure of dispersion?

range

percentile

median

quartile

View answer & explanation

Correct answer is A

No explanation has been provided for this answer.

454.

A chord, 7cm long, is drawn in a circle with radius 3.7cm. Calculate the distance of the chord from the centre of the circle

0.7cm

1.2cm

2.0cm

2.5cm

View answer & explanation

Correct answer is B

let the chord be AB = 7cm

radius OA = 3.7cm distance of the = OM using Pythagoras theorem

OA² = AM² + OM²

3.7² = 3.5² + OM²

13.69 = 12.25 + OM²

13.69 - 12.25 = OM²

1.44 = OM²

OM = $\sqrt{1.44}$

OM = 1.2cm

distance of chord = 1.2cm

455.

The area of a sector a circle with diameter 12cm is 66cm². If the sector is folded to form a cone, calculate the radius of the base of the cone [Take $\pi = \frac{22}{7}$ ]

3.0cm

3.5cm

7.0cm

7.5cm

View answer & explanation

Correct answer is B

diameter = 12cm

radius = $\frac{12}{2}$ cm = 6cm

area of sector = 66cm²

area of sector = area of cone

66 = $\pi rl$

66 = $\frac{22}{7} \times r \times 6$

divide both sides by 6

11 = $\frac{22}{7}r$

22r = 11 x 7

r = $\frac{77}{22}$

= 3.5cm