Primary 6 PSLE Mathematics Money Quiz

Primary 6 PSLE Mathematics Quiz - Money (Answer Key)

Total Marks: 60

Section A: Multiple-Choice Questions (Questions 1 to 5)

Each question carries 2 marks.

1. Answer: B ($5.10)

• Working: $0.85 × 6 =$5.10
• Explanation: To find the total cost, multiply the cost of one pencil by the number of pencils. $0.85 × 6 =$5.10.
• Marking Notes: 1 mark for correct multiplication, 1 mark for correct answer with dollar sign.

2. Answer: A ($33.60)

• Working: $12.90 +$3.50 = $16.40.$50 - $16.40 =$33.60
• Explanation: First, find the total cost of the items: $12.90 +$3.50 = $16.40. Then, subtract from the$50 note: $50 -$16.40 = $33.60.
• Marking Notes: 1 mark for correct total cost, 1 mark for correct subtraction.

3. Answer: B ($18)

• Working: 25% of $24 =$24 × 25/100 = $6. Sale price =$24 - $6 =$18.
• Explanation: A 25% discount means you pay 100% - 25% = 75% of the original price. 75% of $24 =$24 × 75/100 = $18. Alternatively, find the discount amount: 25$24 = $6, then subtract from$24.
• Marking Notes: 1 mark for correct discount amount, 1 mark for correct sale price.

4. Answer: B ($13.90)

• Working: Apples: 3 × $2.50 =$7.50. Oranges: 2 × $3.20 =$6.40. Total: $7.50 +$6.40 = $13.90.
• Explanation: Calculate the cost of each fruit separately, then add them together.
• Marking Notes: 1 mark for correct cost of apples, 1 mark for correct total.

5. Answer: C ($75)

• Working: Belt cost: $45 -$15 = $30. Total:$45 + $30 =$75.
• Explanation: The belt costs $15 less than the wallet, so the belt costs$45 - $15 =$30. The total cost is $45 +$30 = $75.
• Marking Notes: 1 mark for correct belt cost, 1 mark for correct total.

Section B: Short-Answer Questions (Questions 6 to 15)

Each question carries 3 marks.

6. Answer: $720

• Working:
  • Total number of pens: 50 × 12 = 600 pens
  • Total money collected: 600 × $1.20 =$720
• Explanation: First, find the total number of pens by multiplying the number of boxes by the number of pens per box: 50 × 12 = 600 pens. Then, multiply the total number of pens by the selling price per pen: 600 × $1.20 =$720.
• Marking Notes: 1 mark for total pens, 1 mark for correct multiplication, 1 mark for correct answer.

7. Answer: $38.60

• Working:
  • February savings: $15.50 +$3.80 = $19.30
  • March savings: $19.30 × 2 =$38.60
• Explanation: First, find Siti's savings in February: $15.50 +$3.80 = $19.30. Then, find her savings in March, which is twice the February amount:$19.30 × 2 = $38.60.
• Marking Notes: 1 mark for February savings, 1 mark for correct multiplication, 1 mark for correct answer.

8. Answer: 60 adult tickets

• Working:
  • Let the number of adult tickets be $a$ and children's tickets be $c$.
  • $a + c = 120$ (Equation 1)
  • $6a + 3c = 540$ (Equation 2)
  • Multiply Equation 1 by 3: $3a + 3c = 360$
  • Subtract from Equation 2: $(6a + 3c) - (3a + 3c) = 540 - 360$
  • $3a = 180$
  • $a = 60$
• Explanation: This is a simultaneous equation problem. Let $a$ be the number of adult tickets and $c$ be the number of children's tickets. The total number of tickets is 120: $a + c = 120$. The total money collected is $540:$6a + 3c = 540$. Solve these equations to find$a$.
• Marking Notes: 1 mark for setting up equations, 1 mark for correct method, 1 mark for correct answer.

9. Answer: $140

• Working:
  • Deposit: 30% of $1200 =$1200 × 30/100 = $360
  • Remaining amount: $1200 -$360 = $840
  • Each instalment: $840 ÷ 6 =$140
• Explanation: First, calculate the deposit: 30% of $1200 =$360. Subtract the deposit from the total cost to find the amount to be paid in instalments: $1200 -$360 = $840. Divide this by the number of instalments (6):$840 ÷ 6 = $140.
• Marking Notes: 1 mark for deposit, 1 mark for remaining amount, 1 mark for instalment amount.

10. Answer: $163.20

• Working:
  • Apples sold at $0.80: 3/5 × 240 = 144 apples. Money: 144 ×$0.80 = $115.20
  • Apples sold at $0.50: 240 - 144 = 96 apples. Money: 96 ×$0.50 = $48.00
  • Total money: $115.20 +$48.00 = $163.20
• Explanation: First, find the number of apples sold at $0.80: 3/5 of 240 = 144 apples. The money from these is 144 ×$0.80 = $115.20. The remaining apples are 240 - 144 = 96, sold at$0.50 each, giving 96 × $0.50 =$48.00. The total is $115.20 +$48.00 = $163.20.
• Marking Notes: 1 mark for number of apples at each price, 1 mark for correct money from each group, 1 mark for correct total.

11. Answer: $60

• Working:
  • Discount: 20% of $75 =$75 × 20/100 = $15
  • New price: $75 -$15 = $60
• Explanation: A 20% reduction means you pay 80% of the original price. 80% of $75 =$75 × 80/100 = $60. Alternatively, find the discount: 20$75 = $15, then subtract:$75 - $15 =$60.
• Marking Notes: 1 mark for discount amount, 1 mark for correct new price, 1 mark for correct answer.

12. Answer: $60

• Working:
  • Total parts: 3 + 5 = 8 parts
  • Value of 1 part: $240 ÷ 8 =$30
  • Ali's share: 3 × $30 =$90
  • Ben's share: 5 × $30 =$150
  • Difference: $150 -$90 = $60
• Explanation: The ratio 3:5 means the total is divided into 3 + 5 = 8 equal parts. Each part is worth $240 ÷ 8 =$30. Ali gets 3 parts ($90) and Ben gets 5 parts ($150). Ben receives $150 -$90 = $60 more.
• Marking Notes: 1 mark for total parts, 1 mark for value of 1 part, 1 mark for correct difference.

13. Answer: $19.20

• Working:
  • Total cost: $18.50 +$12.30 = $30.80
  • Change: $50 -$30.80 = $19.20
• Explanation: Add the cost of the flour and sugar: $18.50 +$12.30 = $30.80. Subtract this from the$50 note: $50 -$30.80 = $19.20.
• Marking Notes: 1 mark for total cost, 1 mark for correct subtraction, 1 mark for correct answer.

14. Answer: $10.40

• Working:
  • First kilometre: $3.20
  • Additional kilometres: 10 - 1 = 9 km
  • Cost for additional km: 9 × $0.80 =$7.20
  • Total fare: $3.20 +$7.20 = $10.40
• Explanation: The first kilometre costs $3.20. The remaining 9 kilometres (10 - 1 = 9) cost$0.80 each: 9 × $0.80 =$7.20. The total fare is $3.20 +$7.20 = $10.40.
• Marking Notes: 1 mark for number of additional km, 1 mark for cost of additional km, 1 mark for correct total.

15. Answer: $1400

• Working:
  • Total salary for two workers: 2 × $1800 =$3600
  • Third worker's salary: $5000 -$3600 = $1400
• Explanation: The total budget is $5000. Two workers earn$1800 each, so they earn a total of 2 × $1800 =$3600. The third worker earns the remainder: $5000 -$3600 = $1400.
• Marking Notes: 1 mark for total of two workers, 1 mark for correct subtraction, 1 mark for correct answer.

Section C: Problem-Solving Questions (Questions 16 to 20)

Each question carries 5 marks.

16. Answer: $873.12

• Working:
  • Discount: 15% of $960 =$960 × 15/100 = $144
  • Price after discount: $960 -$144 = $816
  • GST: 7% of $816 =$816 × 7/100 = $57.12
  • Final price: $816 +$57.12 = $873.12
• Explanation: First, calculate the 15% discount: 15% of $960 =$144. The discounted price is $960 -$144 = $816. Then, calculate the 7$816 = $57.12. The final price is$816 + $57.12 =$873.12.
• Marking Notes: 1 mark for discount amount, 1 mark for price after discount, 1 mark for GST amount, 1 mark for final price, 1 mark for correct answer.
• Common Mistake: Students may incorrectly calculate GST on the original price ($960) instead of the discounted price ($816).

17. Answer: $440

• Working:
  • Total revenue: 40 × $25 =$1000
  • Total cost of making cakes: 40 × $12 =$480
  • Total expenses: $480 +$80 = $560
  • Profit: $1000 -$560 = $440
• Explanation: First, calculate the total revenue from selling 40 cakes: 40 × $25 =$1000. Then, calculate the total cost of making the cakes: 40 × $12 =$480. Add the rental cost: $480 +$80 = $560. Profit is revenue minus total expenses:$1000 - $560 =$440.
• Marking Notes: 1 mark for revenue, 1 mark for cost of cakes, 1 mark for total expenses, 1 mark for profit, 1 mark for correct answer.
• Common Mistake: Students may forget to include the rental cost in the expenses.

18. Answer: $20

• Working:
  • Total cost of present: 5 × $12 =$60
  • Number of friends who actually pay: 5 - 2 = 3 friends
  • Amount each pays: $60 ÷ 3 =$20
• Explanation: First, find the total cost of the present: 5 friends × $12 each =$60. Since 2 friends cannot pay, the remaining number of friends paying is 5 - 2 = 3. Each of these 3 friends pays $60 ÷ 3 =$20.
• Marking Notes: 1 mark for total cost, 1 mark for number of paying friends, 1 mark for correct division, 1 mark for correct answer, 1 mark for clear working.
• Common Mistake: Students may incorrectly divide by 5 instead of 3.

19. Answer: 15 blue pens and 15 red pens

• Working:
  • Let $b$ be the number of blue pens and $r$ be the number of red pens.
  • $b + r = 30$ (Equation 1)
  • $1.50b + 2.20r = 51$ (Equation 2)
  • Multiply Equation 1 by 1.50: $1.50b + 1.50r = 45$
  • Subtract from Equation 2: $(1.50b + 2.20r) - (1.50b + 1.50r) = 51 - 45$
  • $0.70r = 6$
  • $r = 6 ÷ 0.70 = 8.57...$ (This gives a non-integer, so let's try another method)
  • Alternative Method (Guess and Check):
    • If 15 blue and 15 red: 15 × $1.50 + 15 ×$2.20 = $22.50 +$33.00 = $55.50 (Too high)
    • If 20 blue and 10 red: 20 × $1.50 + 10 ×$2.20 = $30.00 +$22.00 = $52.00 (Too high)
    • If 25 blue and 5 red: 25 × $1.50 + 5 ×$2.20 = $37.50 +$11.00 = $48.50 (Too low)
    • If 22 blue and 8 red: 22 × $1.50 + 8 ×$2.20 = $33.00 +$17.60 = $50.60 (Too low)
    • If 23 blue and 7 red: 23 × $1.50 + 7 ×$2.20 = $34.50 +$15.40 = $49.90 (Too low)
    • If 21 blue and 9 red: 21 × $1.50 + 9 ×$2.20 = $31.50 +$19.80 = $51.30 (Too high)
    • If 20 blue and 10 red: $52.00 (Too high)
    • If 19 blue and 11 red: 19 × $1.50 + 11 ×$2.20 = $28.50 +$24.20 = $52.70 (Too high)
    • If 18 blue and 12 red: 18 × $1.50 + 12 ×$2.20 = $27.00 +$26.40 = $53.40 (Too high)
    • If 17 blue and 13 red: 17 × $1.50 + 13 ×$2.20 = $25.50 +$28.60 = $54.10 (Too high)
    • If 16 blue and 14 red: 16 × $1.50 + 14 ×$2.20 = $24.00 +$30.80 = $54.80 (Too high)
    • If 15 blue and 15 red: $55.50 (Too high)
    • The pattern shows that as the number of blue pens increases, the total cost decreases. Let's try more blue pens:
    • If 28 blue and 2 red: 28 × $1.50 + 2 ×$2.20 = $42.00 +$4.40 = $46.40 (Too low)
    • If 26 blue and 4 red: 26 × $1.50 + 4 ×$2.20 = $39.00 +$8.80 = $47.80 (Too low)
    • If 24 blue and 6 red: 24 × $1.50 + 6 ×$2.20 = $36.00 +$13.20 = $49.20 (Too low)
    • If 22 blue and 8 red: $50.60 (Too low)
    • If 20 blue and 10 red: $52.00 (Too high)
    • The correct combination is between 22 blue/8 red and 20 blue/10 red. Since the total must be exactly $51, and the numbers must be whole, let's check 21 blue and 9 red:$51.30 (Too high). 22 blue and 8 red: $50.60 (Too low). There is no whole number solution that gives exactly$51. Let's re-examine the problem.
    • Correction: The problem statement might have a slight error. Let's adjust the total cost to $50.60 or$51.30 to make it work. For the purpose of this answer key, we will assume the intended answer is 22 blue pens and 8 red pens, giving a total of $50.60. However, to match the given total of$51, we can use 21 blue and 9 red ($51.30) or 20 blue and 10 red ($52.00). Since none match exactly, we will provide the closest possible answer with a note.
    • Corrected Problem: Let's assume Mrs Lim spent $50.60. Then 22 blue and 8 red pens.
    • **For the original problem ($51):** The closest whole-number solution is 21 blue and 9 red ($51.30) or 22 blue and 8 red ($50.60). Neither is exact. This highlights the importance of checking answers.
    • Let's solve using algebra correctly:
      • $b + r = 30$
      • $1.5b + 2.2r = 51$
      • Multiply first equation by 1.5: $1.5b + 1.5r = 45$
      • Subtract: $(1.5b + 2.2r) - (1.5b + 1.5r) = 51 - 45$
      • $0.7r = 6$
      • $r = 6 / 0.7 = 60/7 = 8.57...$
      • Since the number of pens must be a whole number, there is no exact solution. This means the problem as stated has no integer solution. For teaching purposes, we will use the closest integer solution: 21 blue and 9 red ($51.30) or 22 blue and 8 red ($50.60). The intended answer is likely 21 blue and 9 red, as it is closer to $51.
    • Final Answer for this key: 21 blue pens and 9 red pens (total $51.30, closest to$51).
• Explanation: This is a system of equations problem. Let $b$ be the number of blue pens and $r$ be the number of red pens. The total number of pens is 30: $b + r = 30$. The total cost is $51:$1.50b + $2.20r = 51$. Solving these equations gives a non-integer solution, indicating a slight issue with the problem's numbers. The closest whole-number solution is 21 blue and 9 red pens.
• Marking Notes: 1 mark for setting up equations, 1 mark for correct method, 1 mark for attempting to solve, 1 mark for identifying the closest whole-number solution, 1 mark for final answer.
• Common Mistake: Students may not check if their answer is a whole number.

20. Answer: 60 employees

• Working:
  • Let the number of Grade A employees be $x$, Grade B be $2x$, and Grade C be $3x$.
  • Total bonus paid: $600x + 400(2x) + 200(3x) = 600x + 800x + 600x = 2000x$
  • This equals $36,000:$2000x = 36000$
  • $x = 36000 ÷ 2000 = 18$
  • Number of Grade A: 18
  • Number of Grade B: 2 × 18 = 36
  • Number of Grade C: 3 × 18 = 54
  • Total employees: 18 + 36 + 54 = 108
• Explanation: The ratio of employees is 1:2:3. Let the number of Grade A employees be $x$. Then Grade B has $2x$ and Grade C has $3x$. The total bonus paid is $600x +$400(2x) + $200(3x) =$600x + $800x +$600x = $2000x$. This equals $36,000, so$2000x = 36000$, and$x = 18$. The total number of employees is$x + 2x + 3x = 6x = 6 × 18 = 108$.
• Marking Notes: 1 mark for setting up variables, 1 mark for total bonus expression, 1 mark for solving for x, 1 mark for total employees, 1 mark for correct answer.
• Common Mistake: Students may forget to multiply the number of employees by the bonus amount for each grade.