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 =14Required percentage =14x 100% = 20%.70Video Explanation:https://youtu.be/cBamI6iRNIA