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Per NCERT, a child arranges marbles in rows: 1 marble in row 1, 2 in row 2, 3 in row 3, ..., 25 in row 25. How many marbles total?
A325 (= 25 × 26 / 2)
B255
C250
D625
Answer & Solution
Correct answer: A. 325 (= 25 × 26 / 2)
Per NCERT Exercise 8.2.7, total = 1+2+...+25 = S₂₅ = 25 × 26 / 2 = 325.
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