Aptitude - Percentage - Discussion

They given unit digit is 1 or 9.

Suppose take 13 it is 169 so here unit digit is 9 so why it is not correct?

What is mean by unit digit?

Hai raju I can solve your problem:

Let us consider the number be = x.

25%of that number = 25*(x/100) = x/4(let us say as y).
And also given that 18% of 650 = 18*(650/100) = 117.

(Once read 1st line of question).

It means that y is less than 117 by 19 so; 117-y = 19.
117-(x/4) = 19.
so x = 392.

In question he said 1 or 9 in the units digit there are 4 numbers between 1 to 10 whose unit digit ends between 1 and 9 they are 1, 3, 7, 9 so tell me that what is the solution?

@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?