# Mathematics 2020 Past Questions | WAEC

Study the following Mathematics past questions and answers for JAMB, WAEC NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

31. In the diagram, PS¯/SR¯, PS¯/TR¯, QS¯/UR¯, PS¯= 15cm, SR¯= 8cm, PS¯ = 10cm and area of △ SUR = 24cm^{2}. Calculate the area of PTRS.

**A.**40 cm^{2}**B.**48 cm^{2}**C.**80 cm^{2}

**D.** 120 cm^{2}

**Correct Option: Answer is C**

Area PTRS = 10cm x 8cm

= 80cm

**32. **In the diagram, PQR is a circle with centre O. If < OPQ = 48^{o}, find the value of m

**A.**96^{o}**B.**90^{o}**C.**68^{o}**D.**42^{o}

**Correct Option: Answer is A**

Q

< OQP = 48^{o} (base angles of isoceles △)

m = 48^{o} + 48^{o} = 96^{o} (exterior angle of a △)

**33. **The pie chart shows the population of men, women, and children in a city. If the population of the city is 1,800,000, how many men are in the city?

**A.**845,000**B.**600,000**C.**355,000

**D. 250,000**

**Correct Option: Answer is B**

Angle of Men = 360^{o} – (120 + 169)

= 360^{o} – 289^{o} = 71^{o}

Number of men = 71/360 x 1800,000

= 355,000

**34. **The mean of the numbers 15, 21, 17, 26, 18, and 29 is 21. Calculate the standard deviation

**A.**9**B.**6**C.**5**D.**0

**Correct Option: Answer is C**

**35. **In the diagram, O is the centre of the circle. SOQ is the diameter and < SRP = 37^{o}. Find < PSQ.

**A.**127^{o}**B.**65^{o}**C.**53^{o}**D.**37^{o}

**Correct Option: Answer is C**

< PSQ = 180^{o} – (37^{o} + 90^{o})

= 180^{o} – 127^{o} = 53^{o}

**36. **Find the sum of the interior angle of a pentagon.

**A.**340^{o}**B.**350^{o}**C.**540^{o}**D.**550^{o}

**Correct Option: Answer is C**

- Sum of interior angles = (n − 2) × 180∘

= (5 – 2) x 180^{o}

= (5 – 2) x 180^{o} = 3 x 180^{o}

= 540^{o}

**37. **The diameter of a sphere is 12 cm. Calculate, correct of the nearest cm^{3}, the volume of the sphere, [Take π=22/7]

903 cm

A.^{3}**B.**904 cm^{3}**C.**905 cm^{3}**D.**906 cm^{3}

**Correct Option: Answer is C**

Volume of Sphere (V) = 4/3 πr^{3}

Diameter = radius x 2, r = =12/2 6cm

V = 4/3 x 22/7 x 6 x 6 x 6 = 905.14 = 905cm^{3}

**38. **A box contains 12 identical balls of which 5 are red, 4 blue, and the rest are green. If a ball is selected at random from the box, what is the probability that it is green?

**A.**3/4**B.**1/2**C.**1/3**D.**1/4

**Correct Option: Answer is D**

No. of red = 5

No. of blue = 4

No. of green = 3

Total = 12

Pr(Green) = 3/12=1/4

**39. **A box contains 12 identical balls of which 5 are red, 4 blue, and the rest are green. If two balls are selected at random one after the other with replacement, what is the probability that both are red?

**A.**25/144**B.**5/33**C.**5/6**D.**103/132

**Correct Option: Answer is A**

- Pr (R)= 5/12
- Pr (B)= 4/12
- Pr (G)= 3/12
- Therefore:
- Pr (RR)= 5/12 x 5/12 x 5/12 =25/144

**40. **In the diagram PQ is a straight line. If m = 1/2(x + y + z), find value of m.

**A.**45^{o}**B.**60^{o}**C.**90^{o}**D.**100^{o}

**Correct Option: Answer is B**

x + y + m + 2 = 180\(^o\)

\(\frac{x + y + 2}{2} + \frac{m}{2}\) = 90\(^o\)

m + \(\frac{m}{2} = 90^o\)

3m = 2 x 90\(^o\)

\(\frac{3m}{3} = \frac{180^o}{3}\)

m = 60\(^o\)

**41. **

x | 6.20 | 6.85 | 7.50 |

y | 3.90 | 5.20 | 6.50 |

The points on a linear graph are as shown in the table. Find the gradient (slope) of the line.

**A.**2 1/2**B.**2**C.**1**D.**1/2

**Correct Option: Answer is B**

**42. **In the diagram, O is the centre of the circle, PQ¯and RS¯are tangents to the circle. Find the value of (m + n).

**A.**120^{o}**B.**90^{o}**C.**75^{o}**D.**60^{o}

**Correct Option: Answer is B**

m + n + 90^{o} + 180^{o} (sum of angle in a △)

m + n = 180^{o}^{ }– 90^{o}

m + n =90^{o}

**43. **Which of the following is not a sufficient condition for two triangles to be congruent?

**A.**AAS**B.**SSS**C.**SAS**D.**SSA

**Correct Option: Answer is D**

**44. **A woman received a discount of 20% on a piece of cloth she purchased from a shop. If she paid $525.00, what was the original price?

**A.**$675.25**B.**$660.25**C.**$656.25**D.**$616.25

**Correct Option: Answer is C**

Let the cost of the cloth be x

Then 20% of x =20/100x =1/5x

x/5=x-525

= 5(x-525)=x

5x – 2625 =x

X=2625/4 = 656.25

**45. **The interquartile range of distribution is 7. If the 25th percentile is 16, find the upper quartile.

**A.**35**B.**30**C.**23**D.**9

**Correct Option: Answer is C**

Q3 = ¾(n + 1)^{th}

Q3 -Q1 =7

Q3 -16 =7

Q3 = 7 +16

=23