(1):连续十个数中,有一个个位数是四;个位上的四共有600/10=60个;(2):十位上的四共有:40,41,42...49;140,141,142...149;240,241,242...249;340,341,342...349;440,441,442...449;540,541,542..549;有10*6=60个;(3):百位上的四有400,401,402...499共100个;合计:60+60+100=220
