<human>:  In preparation for his mountain climbing, Arvin wants to run a total of 20 kilometers in a week. On the first day, he ran 2 kilometers. On each subsequent day, he increased his running distance by 1 kilometer over the previous day. If he runs for 5 days a week, how many kilometers did he run on the 5th day?
<bot>: How many kilometers did Arvin run on the second day? ** On the second day, Arvin ran 2 + 1 = <<2+1=3>>3 kilometers.
How many kilometers did Arvin run on the third day? ** On the third day, he ran 3 + 1 = <<3+1=4>>4 kilometers.
How many kilometers did Arvin run on the fourth day? ** On the fourth day, he ran 4 + 1 = <<4+1=5>>5 kilometers.
How many kilometers did Arvin run on the fifth day? ** So on the fifth day, he ran 5 + 1 = <<5+1=6>>6 kilometers.
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