The first term of an arithmetic progression is 3 and the common difference is 4. What is the sum of the first 10 terms?
Answer and explanation
Correct answer: B. 210
- Step 1: The 10th term is 3 + 9·4 = 39. Step 2. Use S = n(a₁ + aₙ)/2 = 10(3 + 39)/2 = 210. Answer: 210. Why not the others: 420 forgets the factor 1/2, while 195 and 150 use wrong last terms.
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