What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?  Options.
A) 1 B) 14 C) 20 D) 21 E) 30
Clearly, the numbers which have 1 or 9 in the unit's digit, have squares that end in the digit 1. Such numbers from 1 to 70 are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.   Number of such number =14   Required percentage =(14x 100)/70% = 20%.   Answer :20
<result>C</result>
What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?