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Combine a capped geometric plan with arithmetic increments

A student with a knee problem plans swimming and jogging to prepare for a 2.4 km NAPFA run. On day 1 he jogs 200200 m and swims 200200 m. From day 2, jogging rises by 20%20\% of the previous day’s distance but is capped at 400400 m per day; swimming increases by 5050 m each day. Find the combined distance after 20 days, and the first day his combined daily distance reaches 2.42.4 km.

[2012/PJC/Promo/8]

CJC · Discussion · Question 17

Separate the uncapped first four jogs from the later fixed distance.

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