If 1+22+333+4444+55555+666666+7777777+88888888is congruent to n modulo 9, where 0≤n<9, then what is the value of n?
Solution — click to reveal
A number is congruent to the sum of its digits (mod9). Thus, 1+22+333+4444+55555+666666+7777777+88888888≡1+4+9+16+25+36+49+64≡1+4+0+7+7+0+4+1=24≡6(mod9).