<human>:  Bob has planted corn in his garden, and it has just started to sprout. A week after planting it, it had grown 2 inches. The next week, its height increased by twice as much as it had the first week. In the third week, it grew 4 times as much as it did the week before. How tall are the corn plants now?
<bot>: How tall was the corn plant in the second week? ** The second week it grew twice as much as the first week, so 2 * 2 inches = <<2*2=4>>4 inches.
How tall was the corn plant in the third week? ** The third week it grew 4 times as much as in the second week, so 4 * 4 inches = <<4*4=16>>16 inches.
How tall are the corn plants now? ** In total, it grew 2 inches + 4 inches + 16 inches = <<2+4+16=22>>22 inches.
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