A number of 50 digits has all its digits equal to 1 except the 26th digit. If the number is divisible by 13, then find the digit in the 26th place.
1001=7*11*13
so A=111111 = 111*1001 is divisible by 13
our number can be written AAAA1XAAAA
X= the 26th digit
SINCE AAAA is divisible by 13
we are left with simple problem 1X -FOR WHAT VALUE IF X IS 1X DIVISIBLE BY 13??
The answer of cours is 3 ( three)
ady
so easy
