Aptitude - Percentage - Discussion

Numbers from 1 to 70.

1 unit digit -> 1,11,21,31,41,51,61 -> 7 numbers.
9 unit digit -> 9,19,29,39,49,59,69 -> 7 numbers.

So, the total 1 and 9 unit digits is 14 numbers.
Now percentage;
14/70 * 100 = 20%.

Very helpful explanation, Thanks. @Tabi.

@All.

Here is my explanation for the answer.

Let's take initial values as 100%, which means initially the fruit seller had some apples, so I take that as 100%.

Now, if he sells 40% of his apples, he has 60% of the apples remaining.

So, in the question, they have already stated that the seller has 420 apples after selling 40%.

Thus, we have:
60% = 420.
100% = x.

To solve this expression:
x = (420×100)60x = 60(420×100)​.
x = 700x = 700.

Therefore, the answer is 700.

In every ten numbers, we have only two numbers that end with digits 1 or 9.
So b/w 1 to 70 we 14. (7*2 = 14).
Here 7 represents no of tens and 2 represents no of numbers that end with digit 1 or 9.
So, 14/70 * 100 = 20.

What is the unit's digit? Please explain me.

Why don't we consider the 12, 13, 18 because it has 1 as a unit digit?

@All.

Unit place is the first digit and not the last. As per the place value system it would always begin from left to right. This is simply a wrongly phrased question.

There are 10 digits from 0 to 9 total( 10 nos) out of which 1 and 9 are asked in question (2 digits) so in question at units place Bo's are not repeating.

Hence 2 digits out of 10 digits Make it 20%(2/10=20%).

Am I right?

@Moses Ug.

We can't consider 12 to 18 because the question says in units place of a number it should either have 1 or 9 not in tens place.

The unit's digit (or ones digit) of a number is the digit in the farthest right position. It represents how many ones are in the number.

For example:
In the number 345, the unit's digit is 5.
In the number 82, the unit's digit is 2.
In the number 1090, the unit's digit is 0.
So, when looking for numbers with a specific unit's digit, you're checking the last digit of each number.