8 higher-order questions on the Class 10 syllabus, set out like a 25-mark, 1-hour paper. Try it in one sitting, then open each worked solution to mark your work.
25 marks
1 hour
8 questions
No calculator
Our own practice paper, not a CBSE paper. CBSE has not yet published a sample paper, blueprint or Class 10 syllabus for Mathematics Advanced, so we wrote these questions ourselves on the current Class 10 chapters, at the higher-order (HOTS) level CBSE says the paper will have. What CBSE has said about the paper.
Instructions
All questions are compulsory. Marks are shown with each question.
Calculators are not allowed. Leave answers in surd form or in terms of π unless a question says otherwise.
Show your working: in the solutions, marks in brackets show where the method marks go.
Time: 1 hour. Try the whole paper before you open any solution.
Question 1
Real Numbers2 marks
Find the smallest natural number that leaves a remainder of 7 when divided by 12, by 15 and by 20, and is also divisible by 11.
Worked solution
Answer: 187
LCM(12, 15, 20) = 2² × 3 × 5 = 60, so the number is 60k + 7 for a whole number k. [1]
Equal roots means the discriminant is zero: (b − c)² − 4(a − b)(c − a) = 0. [1]
Put u = a − b and w = c − a. Then b − c = −(u + w), and the condition becomes (u + w)² − 4uw = (u − w)² = 0. [1]
So u = w: a − b = c − a, which gives 2a = b + c. [1]
A quicker route: the coefficients add up to 0, so x = 1 is a root. With equal roots both roots are 1, so their product (c − a)/(a − b) = 1, which gives the same result.
Question 6
Statistics3 marks
The median of the distribution below is 28 and the total frequency is 60. Find x and y.
Class
0–10
10–20
20–30
30–40
40–50
Frequency
5
x
20
15
y
Worked solution
Answer: x = 9, y = 11
N = 60, so N/2 = 30. The median 28 lies in the class 20–30, so l = 20, h = 10, f = 20 and cf = 5 + x. [1]
28 = 20 + [(30 − (5 + x))/20] × 10, so 8 = (25 − x)/2 and x = 9. [1]
5 + 9 + 20 + 15 + y = 60 gives y = 11. [1]
Check: the cumulative frequencies are 5, 14, 34, 49, 60, and 30 falls between 14 and 34, so 20–30 really is the median class.
Question 7
Areas Related to Circles5 marks
Three circles, each of radius 7 cm, are drawn in a plane so that each circle touches the other two from outside.
Explain why the centres of the circles form an equilateral triangle, and give its side.
Find the area of the region enclosed between the three circles. Take π = 22/7, and give the answer in the form p√3 − q, then as a decimal using √3 = 1.73.
Find the perimeter of this region.
Worked solution
Answer: (a) side 14 cm; (b) (49√3 − 77) cm² ≈ 7.77 cm²; (c) 22 cm
(a) When two circles touch from outside, the distance between their centres is the sum of the radii: 7 + 7 = 14 cm. All three distances are 14 cm, so the centres form an equilateral triangle of side 14 cm. [1]
(b) Area of the triangle = (√3/4) × 14² = 49√3 cm². [1]
Each angle of the triangle is 60°, so inside the triangle each circle covers a sector of 60°. The three sectors together: 3 × (60/360) × (22/7) × 7² = (1/2) × 154 = 77 cm². [1]
(c) The boundary is three arcs, each 60° of a circle of radius 7 cm: 3 × (60/360) × 2 × (22/7) × 7 = 22 cm. [1]
Question 8
Circles5 marks
Prove that the lengths of the two tangents drawn from an external point to a circle are equal.
The incircle of triangle ABC touches BC, CA and AB at D, E and F. AB = 12 cm, BC = 8 cm and CA = 10 cm. Find AF, BD and CE.
Show that in any triangle, AF = s − BC, where s is half the perimeter, and check it with your answer to part (b).
Worked solution
Answer: (a) proof; (b) AF = 7 cm, BD = 5 cm, CE = 3 cm; (c) s = 15, 15 − 8 = 7
(a) Let PA and PB be tangents from P to a circle with centre O, touching it at A and B. Join OA, OB and OP. OA ⊥ PA and OB ⊥ PB (a tangent is perpendicular to the radius at the point of contact). In right triangles OAP and OBP: OA = OB (radii) and OP is common, so the triangles are congruent (RHS) and PA = PB. [2]
(b) By part (a), let AF = AE = x, BF = BD = y, CD = CE = z. Then x + y = 12, y + z = 8, z + x = 10. Adding: 2(x + y + z) = 30, so x + y + z = 15. [1]
Hence AF = x = 15 − 8 = 7 cm, BD = y = 15 − 10 = 5 cm, CE = z = 15 − 12 = 3 cm. [1]
(c) In general 2(x + y + z) = AB + BC + CA = 2s, so x + y + z = s and AF = x = s − (y + z) = s − BC. Here s = 15 and 15 − 8 = 7 = AF. [1]