Question

What percentage of numbers from 1 to 50 have 1 or 9 in the unit's digit?

• A. 12.5%
• B. 15%
• C. 17.5%
• D. 20%

Answer 1

The correct option is D

20%

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 50 are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49

Number of such numbers = 10

$\therefore Requiredpercentage=\frac{10}{50}\times 100=20$