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  4. The tens digit of 1!+2!+3!+ ldots +49! is

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Q. The tens digit of $1!+2!+3!+\ldots +49!$ is

NTA AbhyasNTA Abhyas 2022

Solution:

$1!+2!+3!+4!=33$ Also $5!=120, \, 6!=720, \, 7!=5040, \, 8!=40320 \, \, and \, \, 9!=326880$
The tens digit of $1!+2!+3!+\ldots +9!=1$
Also note that n! is divisible by 100 for $n\geq 10$ so that tens digit of $10!+11!+\ldots +49!$ is zero
Therefore, tens digit of $1!+2!+3!+\ldots +49!$ is 1.