Aptitude - Percentage - Discussion

@Nicky.

I think you know what is unit's digit?

So from the given question, we have to count the numbers between 1-70.

Which have 1 and 9 in their unit's digit. They are:

1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69 these are numbers we are looking for. And these are having only 1 and 9 in their unit's digit.

So the count of the above numbers is 14.

Then we have calculate the percentage of 14 in 70.

So we assume the percentage is x.

Hence (x/100)*70 = 14.

70x/100 = 14.
70x = 1400.
x = 1400/70 = 20.
x = 20%.

Why don't you take 12, 13, 14...?

Hello friends! in the question, not mentioned that the word "square".

Hello friends here they asked just between numbers from 1 to 70 so we followed this procedure. It is not easy to find if they asked for larger numbers like 1 to 10000 like this. In this case can't keep go on counting so please tell a new shortcut method.

What about 12 13 14, 15, 16, 17, 18?

7x7= 49.

4(9) why don't we count 7 then?

Thanks guys I've got the first question so clearly.

Then what about the numbers of 11, 12, 113, 14, 15, 19 even 1 is their, then why it is not considered?

Y is less than 117 by 19, means; Either y =117 - 19 or 117 - y = 19.

I'm confused with this. Please answer this.

Please read the question carefully.

It says about that number which put in place of a unit and which must be 1 or 9.

So only these number are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.

So total 14 numbers.