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

Question: 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

Answer: Option C

Explanation:

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	x 100	% = 20%.
		70

Video Explanation: https://youtu.be/cBamI6iRNIA