(x + 1) must be a multiple of 2, 3, 4, ..., 9.

(x + 1) is therefore a multiple of the smallest common multiple of these numbers, that is, a multiple of

2 x 2 x 3 x 3 x 5 x 7 = 2520.Let x + 1 = k(2520), k being a whole number.

x = k(2520) - 1. Since there are fewer than 5000 demonstrators, k = 1. Hence x = 2519, the number of marchers.

Source: Berrondom, Marie

Categories: Reasoning, Number sense, Arithmetic, Modular arithmetic, Favorite

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