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

@Muskan and @Preethy.

It is being ask the percentage in two conditions:

a) the number should be between 1 to 70.
b) the number selected between 1 to 70, it's square should have digit 1 at the end.

In simple words, for example the number 11 which consists of digit 1 which satisfies the condition (a) and also it's square (i.e) 121 is also having 1 at end which also satisfies the condition (b) so, this number is taken.

Whereas, if we take number 15 which consists of digit 1 in it but it's square (i.e) 225 is not having digit 1 at the end, therefore, it won't be taken.

And that how the numbers 1,9,11,19,21,29,31,39,41,49,51,59,61,69 are taken which are 14 in total.

Therefore, 14/70 * 100 = 20.

To find the percentage of numbers from 1 to 70 that have 1 or 9 in the unit's digit, we first identify all such numbers.

Numbers with 1 in the unit's digit:
1, 11, 21, 31, 41, 51, 61

Numbers with 9 in the unit's digit:
9, 19, 29, 39, 49, 59, 69

Each set has 7 numbers.

Combining both sets, we have:
1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69,
In total, there are 14 numbers from 1 to 70 with either 1 or 9 in the unit's digit.

Percentage = ( Number of desired numbers)/Total numbers × 100.
Percentage = (14/70)× 100 = 20%.
Therefore, 20% of the numbers from 1 to 70 have either 1 or 9 in the unit's digit.

@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%.

@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.

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.

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%.

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.

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.

1 to 9 = 2 digit (1,9) =2.
11 to 70 = [digit1-tens digit2-units].
At unit one place suppose I have put 1 there that means I have the choice to
put 6 digits at the tens place = 6 * 1 = 6.
similarily for 9 also = 6 *1 = 6.

The reason we are taking 6 digits is because it will exceed the range that is given.
So, total = 14,
14 = x /100 * 70,
x = 20%.