What percentage of numbers from 1 to 70 have squares that end in the digit 1?	Choose the correct choice from the following answers:	A) 1	B) 14	C) 17	D) 20	E) None
Solution   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 numbers = 14.   Required percentage = [14 / 70 x 100]%   = 20%.   Answer 20
<result>D</result>
What percentage of numbers from 1 to 70 have squares that end in the digit 1?