Mathematics 2023 Theory — Question 1
1(a) If V is directly proportional to W and V = 50 when W = 16, find: (i) the formula connecting V and W
Model answer
V = kW. 50 = 16k, so k = 50/16 = 25/8. Formula: V = 25W/8.
All 17 questions from the Junior Secondary Certificate Examination (JSCE) Mathematics 2023 Theory paper, with the correct answer and a full explanation for each. Free, no signup needed.
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1(a) If V is directly proportional to W and V = 50 when W = 16, find: (i) the formula connecting V and W
Model answer
V = kW. 50 = 16k, so k = 50/16 = 25/8. Formula: V = 25W/8.
(ii) V when W = 12
Model answer
V = 25 x 12 / 8 = 300/8 = 37.5.
(iii) W when V = 20
Model answer
20 = 25W/8, so W = 20 x 8 / 25 = 160/25 = 6.4.
(b) If √(p x 8 / 5) = 2/3, find the value of p.
Model answer
Square both sides: 8p/5 = 4/9. 72p = 20, so p = 20/72 = 5/18.
(c) The parallel sides of a trapezium are 8cm and 14cm. If the distance between the parallel sides is 10cm, what is the area of the trapezium?
Model answer
Area = 1/2 (a + b) h = 1/2 x (8 + 14) x 10 = 1/2 x 22 x 10 = 110 cm².
2(a) The shadow of a flagpole is 4m long when the altitude of the sun is 54.5°. What is the height of the pole? (Tan 54.5° = 1.4019)
Model answer
tan 54.5° = height / shadow. Height = 4 x 1.4019 = 5.6076 = 5.61m (2 d.p.).
(b) Solve (x − 6)/4 < (−x + 4)/2 − 2. Show the solution on a number line.
Model answer
Multiply by 4: x − 6 < 2(−x + 4) − 8 x − 6 < −2x 3x < 6, so x < 2. Number line: draw a line, place an open circle at 2 and shade (arrow) to the left of 2, for all numbers less than 2.
(c) 1600 people attended a concert, if 80% of them are women and the rest are men, how many more women than men attended the concert?
Model answer
Women = 80/100 x 1600 = 1280. Men = 1600 − 1280 = 320. Difference = 1280 − 320 = 960 more women.
3. Draw the graph of y = 4x − 1 using a scale of 2cm to 1 unit on x-axis and 2cm to 5 units on y-axis. (a) Use the graph to find the value of x when y = 18.
Model answer
Table: x = −1, 0, 1, 2, 3, 4, 5 gives y = −5, −1, 3, 7, 11, 15, 19. Plot the points and join with a straight line (see graph in the Diagram column). From y = 18 on the y-axis, go across to the line, then down to the x-axis: x = 4.75. Check: 4x − 1 = 18, x = 19/4 = 4.75.
(b) POQ is a sector of a circle with angle 60° at the centre. If the sector has an area of 70cm². Find the radius of the circle to 2 d.p. (Take π = 3.142)
Model answer
Area of sector = (θ/360) x πr² 70 = (60/360) x 3.142 x r² r² = 70 x 6 / 3.142 = 420 / 3.142 = 133.67 r = 11.56 cm (2 d.p.).
(c) Evaluate the binary number in base two 111 (110 + 101)
Model answer
110 + 101: 110 (=6) + 101 (=5) = 1011 in base two. 111 x 1011 (in base two): 111 = 7 and 1011 = 11, so 7 x 11 = 77. 77 in base two = 1001101. Answer: 1001101 (base two).
4(a) A friend asked me to think of a number, add 5 to it and then divide the sum by 20. The result is the same as subtracting 4 from the original number and dividing the difference by 15. Find the number.
Model answer
Let the number be x. (x + 5)/20 = (x − 4)/15 15(x + 5) = 20(x − 4) 15x + 75 = 20x − 80 155 = 5x, so x = 31.
(b) How many sides does a polygon with the total angle of 2520° has?
Model answer
Sum of interior angles = (n − 2) x 180° (n − 2) x 180 = 2520 n − 2 = 14, so n = 16 sides.
(c) A woman bought x kg of meat at N50 per kg, y kg of yams at N30 per kg, 8kg of fruits at Nx per kg and 5kg of beans at Ny per kg. How much did the woman spend on these items?
Model answer
Meat = 50x. Yams = 30y. Fruits = 8 x x = 8x. Beans = 5 x y = 5y. Total = 50x + 30y + 8x + 5y = N(58x + 35y).
5(a) The table below gives the number of candidates admitted to army school from five states: Ekiti 20, Kaduna 35, Borno 10, Oyo 25, Abia 30. Represent this information on a bar chart.
Model answer
Draw equal-width bars with equal gaps: Ekiti 20, Kaduna 35, Borno 10, Oyo 25, Abia 30 (see chart in the Diagram column).
(b) What percentage of candidates are from Ekiti State?
Model answer
Total = 20 + 35 + 10 + 25 + 30 = 120. Ekiti = 20/120 x 100 = 16 2/3% (about 16.7%).
(c) If a candidate is selected at random, find the probability that is from neither Borno or Abia State.
Model answer
Borno + Abia = 10 + 30 = 40. Neither = 120 − 40 = 80. P = 80/120 = 2/3.
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