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4024/21 Oct/Nov 2021, Question 1: Everyday Money Problems

Cambridge O Level Mathematics 4024 · Paper 21 (Calculator) · Calculator · 12 marks

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The question, in short

Calculate water charge with 8% tax, gas and electricity costs from daily and unit rates, and compare or convert electricity generation figures across countries and years.

Summarised in our own words. Use the official paper for the exact wording and any diagrams.

Part (a) · 2 marks

Find the total October water charge after adding 8% tax to $84.25.

  1. 1Tax = 8/100 × 84.25 = 6.74
  2. 2Total = 84.25 + 6.74 = $90.99

Answer90.99

Part (bi) · 2 marks

Find the November gas charge in dollars using 960 units over 30 days at 23 cents daily and 4.3 cents per unit.

  1. 1960 × 4.3 + 30 × 23 = 4128 + 690 = 4818 cents
  2. 2= $48.18

Answer48.18

Part (bii) · 3 marks

Find the number of electricity units used when the 30-day charge is $30.80 at 28 cents daily and 16 cents per unit.

  1. 1Daily charges = 30 × 28 = 840 cents
  2. 2Units cost = 3080 − 840 = 2240 cents
  3. 3Units = 2240 ÷ 16 = 140

Answer140

Part (ci) · 1 mark

Find how much more electricity Japan generated than Australia in 2016, giving the answer in standard form.

  1. 11.03 × 10⁶ − 2.43 × 10⁵ = 1 030 000 − 243 000 = 787 000 = 7.87 × 10⁵

Answer7.87 × 10⁵

Part (cii) · 2 marks

Find the percentage increase in Turkey's electricity generation from 2010 to 2016.

  1. 1Increase = 2.62 × 10⁵ − 2.03 × 10⁵ = 0.59 × 10⁵
  2. 20.59/2.03 × 100 = 29.06… ≈ 29.1%

Answer29.1 or 29.06...

Part (ciii) · 2 marks

Find Spain's 2013 electricity generation given a 4% decrease to the 2016 value.

  1. 196% of the 2013 amount = 2.64 × 10⁵
  2. 22013 amount = 2.64 × 10⁵ ÷ 0.96 = 275 000 = 2.75 × 10⁵ GWh

Answer275 000 or 2.75 × 10⁵

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Also searched as: 4024/21/O/N/21 · 4024_w21_qp_21 · 4024 w21 21 · question 1.
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