WAEC Mathematics 2017 past questions
Ten questions from the 2017 WAEC Mathematics paper, with answers and explanations. We hold 40 questions from this paper, and the Skolra app has all of them.
WAEC Mathematics 2017 questions and answers
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1.
The ages of Tunde and Ola are in the ratio 1:2. If the ratio of Ola's age to Musa's age is 4:5, what is the ratio of Tunde's age to Musa's age?
- A5:2
- B4:5
- C2:5Correct
- D1:5
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Answer: C
Step 1: Tunde : Ola = 1 : 2
Step 2: Ola : Musa = 4 : 5
Step 3: Make Ola's value the same in both ratios. The LCM of 2 and 4 is 4.
Multiply the first ratio by 2: Tunde : Ola = 2 : 4Step 4: Combine into a three-way ratio:
Tunde : Ola : Musa = 2 : 4 : 5Step 5: Extract Tunde : Musa = 2 : 5
- A
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2.
The dimensions of water tank are 13cm, 10cm and 70cm. If it is half-filled with water, calculate the volume of water in litres
- A9.1 litres
- B4.55 litresCorrect
- C45.5 litres
- D2.275 litres
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Answer: B
Step 1: Calculate the full volume of the tank:
V = 13 × 10 × 70 = 9100 cm³Step 2: Half-filled volume:
Vhalf = 9100 / 2 = 4550 cm³Step 3: Convert to litres (1 litre = 1000 cm³):
4550 / 1000 = 4.55 litres - A
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3.
If M = {x : 3 x < 8} and N = {x : 8 < x 12}, which of the following is true?
i. 8 M N
ii. 8 M N
iii. M N =
- Ai and ii only
- Bi only
- Cii only
- Diii onlyCorrect
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Answer: D
Analyse the sets:
M = {x : 3 ≤ x < 8} — includes 3 but excludes 8
N = {x : 8 < x ≤ 12} — includes 12 but excludes 8Check each statement:
- i. 8 ∈ M∩N? — 8 ∉ M and 8 ∉ N, so FALSE
- ii. 8 ∈ M∪N? — 8 is in neither set, so 8 ∉ M∪N: FALSE
- iii. M∩N = ∅? — M contains values up to (but not including) 8, and N contains values greater than 8; they share no element: TRUE
Only statement iii is true.
- A
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4.
A stationary boat is observed from a height of 100m. If the horizontal distance between the observer and the boat is 80m, calculate, correct to two decimal places, the angles of depression of the boat from point of observation
- A38.66°
- B51.34°Correct
- C45.00°
- D53.13°
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Answer: B
Step 1: Set up the right triangle.
The angle of depression θ is measured from the horizontal down to the line of sight to the boat.
Opposite side (vertical) = 100 m
Adjacent side (horizontal) = 80 mStep 2: Apply trigonometry.
tan θ = opposite/adjacent = 100/80 = 1.25Step 3: Find the angle.
θ = tan⁻¹(1.25) ≈ 51.34° - A
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5.
In a class of 45 students, 28 offer chemistry and 25 offer Biology. If each student offers at least one of the two subjects, calculate the probability that a student selected at random from the class offers chemistry only.
- A8/45
- B17/45
- C5/9
- D4/9Correct
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Answer: D
Step 1: Find students offering both subjects.
Using the union formula: |C ∪ B| = |C| + |B| − |C ∩ B|
45 = 28 + 25 − |C ∩ B|
|C ∩ B| = 53 − 45 = 8Step 2: Find students offering chemistry only.
Chemistry only = 28 − 8 = 20Step 3: Calculate probability.
P(chemistry only) = 20/45 = 4/9 - A
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6.
Three exterior angles of a polygon are 30, 40 and 60. If the remaining exterior angles are 46 each, name the polygon.
- AHeptagon
- BNonagon
- CHexagon
- DOctagonCorrect
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Answer: D
Step 1: Sum of exterior angles of any polygon = 360°.
Step 2: Find remaining angles.
Known angles: 30° + 40° + 60° = 130°
Remaining sum = 360° − 130° = 230°
Number of remaining angles = 230° / 46° = 5Step 3: Total number of sides.
Total sides = 3 (given angles) + 5 (remaining) = 8
A polygon with 8 sides is an Octagon - A
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7.
A circular pond of radius 4m has a path of width 2.5m round it. Find, correct to two decimal places, the area of the path. [Take 22/7]
- A65.36 m²
- B75.43 m²
- C82.50 m²Correct
- D90.25 m²
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Answer: C
Step 1: Identify inner and outer radii.
Inner radius r₁ = 4 m
Outer radius r₂ = 4 + 2.5 = 6.5 mStep 2: Area of path = area of outer circle − area of inner circle.
Area = π(r₂² − r₁²) = (22/7)(6.5² − 4²)
= (22/7)(42.25 − 16)
= (22/7)(26.25)
= 22 × 26.25 / 7
= 577.5 / 7
= 82.50 m² - A
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8.
If the total surface area of a solid hemisphere is equal to its volume, find the radius
- A6 cm
- B3 cm
- C9 cm
- D4.5 cmCorrect
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Answer: D
Step 1: Total surface area of a solid hemisphere = curved surface + flat circular base
= 2πr² + πr² = 3πr²Step 2: Volume of a solid hemisphere = (2/3)πr³
Step 3: Set them equal:
3πr² = (2/3)πr³Step 4: Divide both sides by πr²:
3 = (2/3)rStep 5: Solve for r:
r = 3 × (3/2) = 9/2 = 4.5 cm - A
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9.
Simplify; 3x - (p - x) - (r - p)
- A4x - rCorrect
- B2x - r
- C2x + r
- D4x + r
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Answer: A
Step 1: Expand the brackets (distributing the minus signs):
3x - (p - x) - (r - p) = 3x - p + x - r + pStep 2: Collect like terms:
x terms: 3x + x = 4x
p terms: -p + p = 0
r terms: -rResult: 4x - r
- A
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10.
Evaluate
- A26/15
- B2/5
- C1/2
- D13/15Correct
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Answer: D
Step 1: Convert mixed numbers to improper fractions:
3¼ = 13/4; 1⅗ = 8/5; 11⅓ = 34/3; 5⅓ = 16/3Step 2: Compute the numerator:
(13/4) × (8/5) = 104/20 = 26/5Step 3: Compute the denominator:
34/3 - 16/3 = 18/3 = 6Step 4: Divide:
(26/5) ÷ 6 = 26/30 = 13/15 - A
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