JEE Main 2024 Mathematics question
Let Sₙ denote the sum of first n terms of an arithmetic progression. If S₂₀ = 790 and S₁₀ = 145, then S₁₅ – S₅ is:
Answer: (D)
Solution
S₂₀ = 10(2a + 19d) = 790 gives 2a + 19d = 79, and S₁₀ = 5(2a + 9d) = 145 gives 2a + 9d = 29.
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