Question

The tens digit of 1!+2!+3!+4!+5!+.........+29! is?

Answer 1

Answer:

Step-by-step explanation:

1!+2!+3!+4!+5!+6!+7!+8!+9!+10!+.......+29!

Since,1!+2!+3!+4!=331!+2!+3!+4!=33

After this for 5!,6!,7!5!,6!,7! all ones place will come 0

Hence ones place of 1!+2!+....29!1!+2!+....29! is 3

But for tens place, the tens place will become 0 for factorial of numbers above 10. Hence, we have to add all the tens places for no.s below 10, which is,

3\left( till\quad 4! \right) +2\left( for\quad 5! \right) +2\left( for\quad 6! \right) +4\left( for\quad 7! \right) +2\left( for\quad 8! \right) +8\left( for\quad 9! \right)3(till4!)+2(for5!)+2(for6!)+4(for7!)+2(for8!)+8(for9!)

=21=21