In the sum below BOOB is multiplied by BA and each letter represents a single digit between zero and nine. The dots represent digits for which the letters are not known.
BOOB
BA
KIOKI
TOOT .
I . . . . .
BOOB = 3003 and BA = 37, hence BOOB x BA = 111111.
O = 0, I = 1, K = 2, B = 3, A = 7 and T = 9.