The tens digits of 1! + 2! + 3! + ...... + 49! is?
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Answer:
the tens digits of 1+2+3+4+49
Answered by
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Answer:
Sn=n/2[2n+(n-1) d]
=49/2[2×(49-1) 1]
=49/2[2(48) ]
=49/2(96)
=49(48)
=2352
at the tens= 5
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