MATHEMATICS
PAPER 2
GRADE 12
NSC EXAMS PAST PAPERS AND MEMOS JUNE 2019
MEMORANDUM
QUESTION 1
1.1 | Mean = 48 | ✔ 48 (1) |
1.2 | SD/SA = 22,08 Penalty of 1 mark for incorrect rounding | ✔✔22,08 (2) |
1.3 | Girls performed better. The girls’ mean percentage is bigger than that of boys and the girls standard deviation is smaller than that of boys | ✔Girls ✔Reason (2) |
1.4 | 51 – 48 = 3 ∴each boy’s percentage must be increased by 3. | ✔3 (1) |
1.5 | Boys’ standard deviation will remain the same | ✔remain the same (1) |
| | [7] |
QUESTION 2
2.1 | Ages (in years) | Frequency | Cumulative Frequency | 18 ≤ x < 28 | 4 | 4 | 28 ≤ x < 38 | 10 | 14 | 38 ≤ x < 48 | 14 | 28 | 48 ≤ x < 58 | 17 | 45 | 58 ≤ x < 68 | 12 | 57 | 68 ≤ x < 78 | 3 | 60 |
| | ✔frequency ✔cumulative frequency (2) |
2.2 | | ✔grounding at (0 ; 18) ✔upper limits ✔shape (3) |
2.3 | 48 ≤ x < 58 | ✔answer (1) |
2.4 | 60 – 49 = 11 senior citizens | ✔49 ✔answer(2) |
2.5 | Q1 = 39 Q2 = 50 Q3 = 58 | ✔value of Q1 ✔value of Q2 ✔value of Q3 (3) |
2.6 | | ✔minimum and maximum ✔ box (2) |
| | [13] |
QUESTION 3
3.1.1 | | ✔substitution ✔answer (2) |
3.1.2 | mKM = y2 - y1 x2 - x1 = -4 - 7 7 - 0 = - 11 7 | ✔substitution ✔gradient of KM (2) |
3.1.3 | mLM = y2 - y1 x2 - x1 = -4 - 2 7 - 10 = 2 tan α = 2 ∴ α = 63,43º | ✔gradient of LM ✔ tan α = 2 ✔value of α (3) |
3.1.4 | tanθ = - 11 7 Ref ∠ = 57,53º ∴θ = 122,47º LMK = 122,47º - 63,43º = 59,04º | ✔tanθ = - 11 7 ✔reference angle ✔value of θ ✔value of LMK∧ (4) |
3.2 | | ✔ y = 2x + 7 ✔ y = -x - 1 2 2 ✔value of x ✔value of y OR ✔mKL = -5 10 ✔mNM = -5 10 ✔value of x ✔value of y OR ✔Midpoint of KM = ✔ Midpoint of LN = ✔value of x ✔value of y (4) |
3.3 | mLM × mMN = 2 × (-½) = -1 ∴LMN = 90º OR LMN is a right angle | ✔product of gradients ✔conclusion (2) |
3.4 | LMN = 90º and LMK = 59,04º ∴KMN = 90º - 56,04º = 30,96º Area of KMN = ½ × √170 × 5√5 × sin30,96º =37,50 square units
| ✔KL = NM = 5√5 ✔KM = √170 ✔LMN = 90º and LMK = 59,04º ✔KMN = 30,96º ✔Area of KMN Δ (5) |
| | [22] |
QUESTION 4
4.1 | M (2 ; 4) | ✔value of x ✔value of y (2) |
4.2 | r2 = (5 - 2)2 + (0 - 4)2 = 25 ∴ (x - 2)2 + (y - 4)2 = 25 | ✔ (x - 2)2 ✔ (y - 4)2 ✔25 (3) |
4.3 | mGH = 8 - 0 -1 - 5 = - 8 = - 4 6 3 mtan = 3/4 y - 8 = 3/4(x - 1) ∴y = 3/4x + 35/4 | ✔mGH ✔mtan ✔substitution ✔equation (4) |
4.4 | At J, y = 0 (x - 2)2 + (0 - 4)2 = =25 (x - 2)2 = 9 x - 2 = ±3 x = 5 or x = -1 ∴ J (-1;0) | ✔ y = 0 ✔substitution ✔ x = – 1 (3) |
4.5 | HJG is a right angled triangle (8,6 and 10). So the rotation of J around M will complete a rectangle Hence, j ((-1 + 6; 0 + 8)) = J'(5;8) | ✔value of x ✔value of y (2) |
4.6 | x2 + y2 - 12x - 2y + 17 = 0 x2 - 12x + y2 - 2y = -17 x2 - 12x + 36 + y2 - 2y + 1 = -17 + 36 + 1 (x - 6)2 + (y - 1)2 = 20 Distance between the centres:
∴ the centre lies on the original circle | ✔completing the square ✔factorisation: x ✔factorisation: y ✔distance formula ✔conclusion (5) |
| | [19] |
QUESTION 5
5.1.1 | | (2) |
5.1.2 | sin84º = sin2 × 42º = 2sin42ºcos42º
| ✔double angle ✔expansion ✔substitution (3) |
5.1.3 | sin3º = sin(45º - 42º = sin45ºcos42º - -cos45ºsin42º
| ✔3° = 45° – 42° ✔expansion ✔substitution ✔substitution (4) |
5.2 | sin(x - 450º).tan(180º + x).sin(90º - x) cos(-x) -cos x.tan x.cos x cos x -cos x.sin x cos x -sin x | ✔− cos x ✔ tan x ✔cos x ✔cos x ✔ sin x cos x ✔answer (6) |
5.3.1 | cos (A + B) = cos A cos B - sin A sin B | ✔expansion (1) |
5.3.2 | | ✔compound angle identity ✔cos double angle identity ✔sin double angle identity ✔ (1 - cos2α) (4) |
Related Items
5.4 | | ✔ ✔ cos2 θ = cos2θ - sin2θ ✔substitution ✔standard form ✔values of p OR ✔ 2cos2θ − 1 ✔✔substitution ✔standard form ✔values of p OR ✔ ✔ 1 - 2sin2θ ✔substitution ✔standard form ✔values of p (5) |
| | [25] |
QUESTION 6
6.1 | y∈[-1;1] OR -1 ≤ y ≤ 1 | ✔answer (1) |
6.2 | | g: ✔asymptotes at -90° and 90° ✔x-intercepts ✔shape (3) |
6.3 | 180° | ✔180° (1) |
6.4 | x = – 45° | ✔– 45° (1) |
6.5 | x∈[45º ; 90º) OR 45º ≤ x < 90º | ✔critical values ✔notation (2) |
6.6 | h(x) =sin (x – 45°) + 1 | ✔h(x) =sin (x – 45°) + 1 (1) |
| | [9] |
QUESTION 7
7.1 | InΔ KLN : tan w = h LN LN = h tan w | ✔ LN = h (1) tan w |
7.2 | | ✔correct sine rule ✔substitution ✔isolating LM ✔answer (4) |
7.3 | LM = h sin(y + z) and tan w sin z h = 38m, w = 21º, y = 52º and z = 59 ∴LM = 38.sin(52º + 59º) tan21º sin59º = 107,82m | ✔substitution ✔answer (2) |
| | [7] |
QUESTION 8
8.1 | the centre of a circle | ✔answer (1) |
8.2.1 | AC = 10 cm (line from centre ⊥ chord) | ✔length of AC ✔Reason (2) |
8.2.2 | (x + 5)2 = 102 + x2 x2 + 10x + 25 = 100 + x2 10x = 75 ∴ x = 7,5cm ∴radius = 7,5cm +5cm = 12,5cm | ✔radius = (x + 5) ✔applying Pythagoras theorem ✔value of x ✔length of radius (4) |
| | [7] |
QUESTION 9
9.1 | interior opposite angle | ✔answer (1) |
9.2.1 | R2 = Q2 = 41° (∠s in the same seg) P4 = Q1 = 41° (tan-chord theorem) T1 = P4 = 41° (∠s opp. = sides)/(∠e teenoor gelyke sye) OR T1 = R2 = 41° (tan – chord theorem)/(raaklyn-koord stelling) | ✔Statement ✔Reason ✔Statement ✔Reason ✔Statement ✔Reason (6) |
9.2.2(a) | T2 + 34° = 78° (tan - chord theorem ) ∴T2 = 44° | ✔Statement ✔Reason (2) |
9.2.2(b) | 41° + Q2 + 44° + 34° = 180° ( opp. ∠ s of a cyclic quad.) ∴Q2 = 61° | ✔Statement ✔Reason (2) |
9.2.2(c) | T4 = 41° + 61° ( ext. ∠s of a cyclic quad.) ∴T4 = 102° OR T4 + 44° + 34° = 180° (int.∠s of a Δ) | ✔Statement ✔Reason OR ✔Statement ✔Reason (2) |
9.2.2(d) | W + 41°+ 41° = 180° ( int .∠s of a Δ) ∴ ܹW = 98° | ✔Statement ✔ Reason (2) |
9.2.3(a) | Q2 = 61º and T2 = 44º ∴ Q2 ≠ T2 ∴ QR is not parallel to PT (alt. ∠s are not equal) | ✔Q2 ≠ T2 ✔alt. ∠s are not equal (2) |
9.2.3(b) | R2 + W = 41º + 98º = 139º ≠ 180º ∴ PRTW is not a cyclicquad. (Opp. ∠s are not supp.) | ✔R2 +W ≠ 180º ✔ PRTWis not a cyclicquad. (2) |
9.2.3(c) | R1 = T2 = 44°(∠s in same seg) R1 + R2 = 44° + 41° = 95° ≠ 90° ∴ TQ is not a diameter (∠subt. by TQ is not a right angle) | ✔R1 + R2 ≠ 90º ✔TQ is not a diameter (2) |
| [21] |
QUESTION 10
10.1 | Construction: Draw heights h and l on KR and KS respectively. Join LS and MR Proof:
But: area of ΔLRS = area of ΔMSR Area of ΔKRS = Area of ΔKRS Area of ΔLRS Area of ΔMSR ∴ KR = KS RL SM
| ✔construction ✔ratio of areas ✔ratio of areas ✔same base and same height ✔ Area of ΔKRS = Area of ΔKRS (5) Area of ΔLRS Area of ΔMSR |
10.2.1 | AB = 5 units | ✔5 (1) |
10.2.2(a) | C is common CBA = CFB (both =90°) CAB = CBF (sum of ∠s of Δ) ∴ ΔCBA|||ΔCFB (∠, ∠, ∠) | ✔Statement / Reason ✔Statement / Reason ✔Reason (3) |
10.2.2(b) | CB = CA (|||Δs) CF CB CB2 = CF.CA ∴ CF = CB2 CA | ✔proportion ✔reason ✔ CB2 = CF.CA (3) |
10.2.3 | CF = CB2 CA CF = (12)2 13 ≈ 11units | ✔substitution g ✔length of CF (2) |
10.2.4 | AF = 13 – 11 = 2 unit | ✔length of AF (1) |
10.2.5 | CB = CA = (prop. theorem ; DF||BA ) BD AF 12 = 13 BD 2 ∴ BD = 24 13 CF = CB (prop. theorem ; DF ||BA ) FE BD 11 = 12 FE 24 13 ∴FE = 22 units 13 | ✔proportion ✔reason ✔length of BD ✔proportion ✔length of FE (5) |
| | [20] |
| | |
| | TOTAL: 150 |