Let’s solve each problem step by step.
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Section B, Problem 1:
A DVD costs $30. It is reduced by 15%.
First, find 15% of $30:
15% = 15/100 = 0.15
0.15 × 30 = 4.5
So, the discount is $4.50.
New price = original price – discount
= 30 – 4.50 =
$25.50
✔ Check: 85% of 30 (since 100% - 15% = 85%) → 0.85 × 30 = 25.5 → Correct.
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Problem 2:
House value: $400,000 increases by 10%.
Find 10% of 400,000:
10% = 0.10
0.10 × 400,000 = 40,000
New price = 400,000 + 40,000 =
$440,000
✔ Check: 110% of 400,000 = 1.10 × 400,000 = 440,000 → Correct.
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Problem 3:
Population was 900 in 2001. Increased by 12%.
Find 12% of 900:
12% = 0.12
0.12 × 900 = 108
New population = 900 + 108 =
1,008
✔ Check: 112% of 900 = 1.12 × 900 = 1,008 → Correct.
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Problem 4:
Car bought for $7,500. Sold at 30% profit.
Profit = 30% of 7,500
= 0.30 × 7,500 = 2,250
Selling price = cost + profit
= 7,500 + 2,250 =
$9,750
✔ Check: 130% of 7,500 = 1.30 × 7,500 = 9,750 → Correct.
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Problem 5:
Shopkeeper buys:
- Glass door: $1,500 (excluding tax)
- Counter: $120 (including tax) ← This means we don’t add tax to this one!
Tax rate in 2005: 5%
Only the glass door gets taxed.
Tax on door = 5% of 1,500 = 0.05 × 1,500 = $75
Total spent in 2005:
Door with tax: 1,500 + 75 = $1,575
Counter: $120 (already includes tax)
Total = 1,575 + 120 =
$1,695
✔ Part a answer: $1,695
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Part b: What if tax increased to 20%?
Now, tax on door = 20% of 1,500 = 0.20 × 1,500 = $300
Door with new tax: 1,500 + 300 = $1,800
Counter still: $120
Total now: 1,800 + 120 = $1,920
How much more than before?
1,920 – 1,695 =
$225
✔ Part b answer: $225
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Final Answer:
1) $25.50
2) $440,000
3) 1,008
4) $9,750
5a) $1,695
5b) $225
Parent Tip: Review the logic above to help your child master the concept of percent increase and decrease word problems worksheet.
