Question

what percentage of numbers from 1 to 70 have squares that end in the digit 1.

Answer 1

let first we count how many numbers are there.
the numbers which have 1 or 9 at its unit place will definitely end in the digit 1.
there are 7*2=14 such numbers. for percentage, just device 14by 70 and multiply with 100 .(14/70)*100=20%

Answer 2

The possible numbers are
1,9,11,19,21,29,31,39,41,49,51,59,61,69
Number of such numbers =14
Required Percentage ={(14/70)×100}%=20%