Aptitude - Percentage - Discussion

Look again for the definition of "unit's digit".

If we have (for the sake of example) --> 180.
Then:
1 on '1'80 = hundreds digit.
8 on 1'8'0 = tens digit.
0 on 18'0' = units digit.

Therefore, numbers that fulfill the question "What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?" is numbers that have either '1' or '9' on its "units digit".

Disclaimer: 10, or 12, 13, 14, 15, 16, 17 and 18 did not make it to the answer because even though they have '1' on its component, that '1'is not a "units digit" since our definition above.

The correct numbers are: 1, 9 , 11, 19, 21, 29 , 31, 39, 41, 49, 51, 59, 61, 69.

*Counted -> 14 numbers out of 70's.

Percentage = (14/70)*100% = 20%.
Answer : C

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.

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

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

7x7= 49.

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

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

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.

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

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