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%.

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?

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.

What is mean by unit digit?

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?

25% of a number is less than 18% of 650 by 19. Then the number is?

Please send me the solution.

Here's how it is done:

From 1 to 10---only 2 numbers have 1 & 9 at unit's place i.e.= 1 &9.
Therefore, from 10 to 20---11 and 19 have 1 & 9 at unit's place.

Then from 20 to 30---21, 29.
From 30 to 40---31, 39
From 60 to 70---61, 69.

So what concluded here is that each set has 2 numbers which have
1,9 at unit's place.

Therefore: 7 sets=2*7=total 14 numbers.

As per the given we should count only the digits which end with either 1 or 9(i.e, units place).

Suppose if we consider a no 527.

7 is in units place.
2 in tens place and.
5 is in Hundred's place.
In the same we get 1,9,11,19,21,29....so on 14 digits for the above question.

To be simple:
We have no's end with 1 = 7.
We have no's end with 9 = 7.
So total = 14.

Ans: 14/70*100 = 20%.

We should first understand the question ?

The question asks the numbers with 1 or 9 in the unit digit that is in the last digit or ending with 1 or 9.

12, 13, 14 have 2, 3 and 4 in the unit digit respectively.

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