Thread: find the remainder

find the remainder when-



is divided by 10.

No idea.

i just know the sum of n.n!=(n+1)!-1

Originally Posted by adhyeta

find the remainder when-



is divided by 10.

No idea.

i just know the sum of n.n!=(n+1)!-1

Notice for each term is divisable by 10 so they have a remainder of zero(why)

Now we only need to worry about the first 4 terms

We also don't need to worry about the 4 term (why)

so we get so the remainder is 6

Originally Posted by TheEmptySet

Notice for each term is divisable by 10 so they have a remainder of zero(why)

Now we only need to worry about the first 4 terms

We also don't need to worry about the 4 term (why)

so we get so the remainder is 6

yes for the fourth term too we have 16+4=20 (hence, divisible by 10)

thank you.