What percentage of numbers from 1 to 70 has 1 or 9 in the unit’s digit?
Solution
Correct Answer: Option C
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%.
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