alleryA city of 20,000 people grows at 5 per cent per annum. What is its population after 3 years?
A22,050
B23,000
C23,153
D24,150
Answer & Solution
Correct answer: C. 23,153
1. Population growth compounds, so use A = P (1 + R/100) raised to n.
2. A = 20000 x (21/20) x (21/20) x (21/20).
3. A = 23,152.5 people.
4. Population is a whole number, so the estimate is 23,153.
5. Simple growth of 1,000 a year would give only 23,000, which is the trap.
_Source: syllabus Maths Ch7 'Comparing Quantities', Example 9_
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