allerySum of an AP with first term 7, last term 47 and 9 terms is
A162
B243
C189
D297
Answer & Solution
Correct answer: B. 243
1. Use S_n = n/2 * (a + l).
2. S_9 = 9/2 * (7 + 47).
3. = 9/2 * 54 = 9 * 27.
4. = 243.
_Source: Selina Concise Mathematics Class 10, Ch on Arithmetic Progression (Mistral OCR'd PDF), section on sum formula_
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