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St Nicholas 2025 P6 Maths Prelim — Paper 2 Q9b Solution

Paper 2 · Q9b · 1 mark · Percentage

Question

Using the same electricity rates, (b) In February, the charges of electricity for the Wang family were \$60.05 before GST. How many units of electricity did the Wang family use in February?
Answer: 223 units

Worked solution

  1. First 180 units cost $180 \times \$0.25 = \$45$. Remaining charge $= \$60.05 - \$45 = \$15.05$. Units above 180 $= 15.05 \div 0.35 = 43$. Total units $= 180 + 43 = 223$.

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