What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?
Choose the most appropriate option:
A) 20 B) 21 C) 14 D) 1 E) 6
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*100= 
<gadget id="calculator">14/70*100</gadget>
<output>20</output>
20%   20NSWER 20
<result>A</result>
What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?