Savings start at 50 reais in month 1 and rise by 30 reais each month (50, 80, 110, ...). What is the total saved over 12 months?
Answer and explanation
Correct answer: A. BRL 2,580
- Step 1: Arithmetic progression: a12 = 50 + 11 x 30 = 380. Step 2. Sum = 12 x (50 + 380) / 2 = 2,580. Answer: BRL 2,580. Why not the others: The sum needs the average of first and last terms, not just one term.
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