Maths Olympiad Prep

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Algebra Difficulty 4.0 AIME Find the answer United States

Problem:

In the sequence
1,4,7,10,13,16,19, 1, 4, 7, 10, 13, 16, 19, \ldots
each term is 3 less than the next term. Find the 1000th term of the sequence.

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

Solution:

To get from the first term to the 1000th term, we must add three 999 times. That amounts to adding 39993 \cdot 999 which is 29972997. So the 1000th term is 1+2997=29981 + 2997 = 2998.

Want a route through all this instead of an archive? The track puts 2,000 problems in a working order, from AMC 10 level to the IMO shortlist.

Source: MathNet, licensed CC-BY-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.