Question

Whatpercentage of numbers from 1 to 30 has 1 or 9 in the unit's digit?

Answer 1

20% numbers from 1 to 70 have 1 or 9 in the unit's digit. 1,9,11,19,21,29,31,39,41,49,51,59,61,69 this is that series of numbers .These are total 14 numbers out of 70 so 14/70×100 gives us 20 % occurrence of 1 or 9 at unit place.