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What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?

A. 1%

B. 14%

C. 20%

D. 21%

E. None of these

Answer: Option C

Solution(By Examveda Team)

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
$$ = \left( {\frac{{14}}{{70}} \times 100} \right)\% = 20\% $$

This Question Belongs to Arithmetic Ability >> Percentage

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