What number is missing from this series?
(series = a group or a number of related or similar things)
(series = a group or a number of related or similar things)
1, 3, 7, ? , 21
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Let’s think about this…. |
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the answer
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are you sure?
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The answer is 13!
1+2=3
3+4=7
7+6=13
13+8=21
3, 7, 13, 21