Which number will replace the question mark (?) in the following series?
15, 17, 20, 25, 32, 43, ?
Prime numbers are added in each term to obtain the next one.
15+2 = 17
17+3 = 20
20+5 = 25
25+7 = 32
32+11 =Â 43
43+13 = 56
Hence 56 will come in place of the question mark.
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