A-Level Maths H2 Quiz - Numbers Ratio Proportion (Answer Key)
Topic: Numbers, Ratio & Proportion
Total Marks: 40
Section A: Basic Ratio and Proportion
1. [2 marks]
Ratio flour : sugar : butter = 4:2:1.
Sugar corresponds to 2 parts =350 g → 1 part =175 g.
Total parts =4+2+1=7 → total mass =7×175=1225 g.
Answer: 1225 g.
Teaching note: Divide total known mass by its ratio number to get one part, then multiply by total parts.
2. [2 marks]
x:y=3:5=6:10 (multiply by 2 to match y=10).
y:z=10:7.
Thus x:y:z=6:10:7.
Answer: 6:10:7.
Common mistake: Not making the y values equal before combining.
3. [2 marks]
a∝b⇒a=kb.
18=k×6⇒k=3.
When b=11, a=3×11=33.
Answer: 33.
4. [2 marks]
p∝q1⇒pq=k.
8×3=24=k.
When p=12, 12q=24⇒q=2.
Answer: 2.
5. [2 marks]
Ratio 5:3:4, total parts =12.
Smallest share =3 parts.
3/12×720=180.
Answer: \180$.
Section B: Algebraic Proportion and Applications
6. [2 marks]
y∝x21⇒y=x2k.
4=22k=4k⇒k=16.
Equation: y=x216.
Answer: y=x216.
7. [2 marks]
C=50+kn.
250=50+100k⇒100k=200⇒k=2.
For n=250: C=50+2×250=550.
Answer: \550$.
8. [3 marks]
Original mixture: ratio 3:8, total 44 L → acid =113×44=12 L, water =32 L.
Let a L acid added. New ratio: 3212+a=85.
8(12+a)=5×32=160⇒96+8a=160⇒8a=64⇒a=8.
Answer: 8 L.
Marking: 1 mark setup, 1 mark equation, 1 mark answer.
9. [3 marks]
Speed car 1 =240/3=80 km/h.
Speed car 2 =80×1.2=96 km/h.
Time =240/96=2.5 h=2 h 30 min.
Answer: 2 hours 30 minutes.
Marking: 1 mark speeds, 1 mark time, 1 mark conversion.
10. [2 marks]
3x−22x+1=45
4(2x+1)=5(3x−2)
8x+4=15x−10
14=7x⇒x=2.
Answer: x=2.
Section C: Multi-Step Ratio and Proportion Problems
11. [3 marks]
Rates: A =1/10, B =1/15, C =1/30 per day.
Combined rate =101+151+301=303+2+1=306=51.
Time =5 days.
Answer: 5 days (or 1/51).
Marking: 1 mark rates, 1 mark sum, 1 mark final.
12. [3 marks]
Scale 1:25000 → 8 cm on map =8×25000=200000 cm.
200000 cm=2000 m=2 km.
Answer: 2 km.
Marking: 1 mark multiply, 1 mark cm→m, 1 mark m→km.
13. [3 marks]
Let classes be 7k and 5k.
After move: (7k−10):(5k+10)=3:2.
2(7k−10)=3(5k+10)⇒14k−20=15k+30⇒k=50.
Original: 350 and 250.
Answer: 350, 250.
Marking: 1 mark setup, 1 mark solve, 1 mark states.
14. [3 marks]
Q∝r3⇒Q=kr3.
16=k×23=8k⇒k=2.
When r=5, Q=2×125=250.
Answer: 250.
15. [3 marks]
Let cost = \100.Sellingprice= 125.Reducedby20%of125 = 25→saleprice= 100.Overallprofit= 0%(break−even).∗∗Answer:∗∗0%$ profit (no profit no loss).
Marking: 1 mark cost/SP, 1 mark reduction, 1 mark conclusion.
Section D: Challenging Synthesis
16. [2 marks]
a:b=2:3=8:12; b:c=4:5=12:15 → a:c=8:15.
Answer: 8:15.
17. [3 marks]
A rate =1/6, B rate =1/4.
In 1 h together: (1/6+1/4)=5/12 filled.
Remaining =7/12.
A alone time =(7/12)/(1/6)=3.5 h.
Answer: 3.5 hours.
Marking: 1 mark combined, 1 mark remainder, 1 mark time.
18. [3 marks]
Boys =5k, girls =4k.
Glasses: 0.1×5k=0.5k boys, 0.2×4k=0.8k girls.
Total glasses =1.3k out of 9k → fraction =13/90.
Answer: 9013.
19. [3 marks]
x=kzy.
8=k×312=4k⇒k=2.
When y=18,z=6: x=2×618=6.
Answer: 6.
20. [3 marks]
Let Q get \q.ThenP= 2q,R= q+40.2q + q + q + 40 = 400 \Rightarrow 4q = 360 \Rightarrow q = 90.P= 180,Q= 90,R= 130.∗∗Answer:∗∗P$180,Q$90,R$130$.
Marking: 1 mark let, 1 mark equation, 1 mark values.