class 9 ganita manjari chapter 8 exercise solutions (2026-27) – Discussion Forum

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Kriti

Asked: September 8, 2026In: Class 9 Maths

A child arranges marbles in rows so that the first row has 1 marble, the second has 2 marbles, the third has 3 and so on up to 25 rows. How many marbles does the child use in all?

The marble counts represent the sum of the first 25 natural numbers. Using the sum formula Sn = n(n + 1) / 2 with n = 25, the total calculation is 25 x 26 / 2, which gives 325 marbles.