What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit? Select
A) 17
B) 19
C) 20
D) 21
E) 18
C   20   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 = (14/70 x 100)% = 20%.
<result>C</result>
What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?