Aptitude - Percentage - Discussion
Discussion Forum : Percentage - General Questions (Q.No. 4)
4.
What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?
Answer: Option
Explanation:
Clearly, the numbers which have 1 or 9 in the unit's digit, have squares that end in the digit 1. Such numbers from 1 to 70 are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.
Number of such number =14
 Required percentage = |
 |
14 | x 100 |  % = 20%. |
| 70 |
Video Explanation: https://youtu.be/cBamI6iRNIA
Discussion:
102 comments Page 5 of 11.
Uday said:
9 years ago
We cannot keep 2 digits at a time at a unit place, right. so there should be 1 or 9.
Smithy said:
9 years ago
How to find those 14 numbers in between 1-70 is there any shortcut to find it?
Sarika said:
9 years ago
Clearly, the numbers which have 1 or 9 in the unit's digit, have squares that end in the digit 1. Such numbers from 1 to 70 are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.
Number of such number = 14.
I.E.
100% -------> 70 number.
X --------> 14.
(100x14) / 70 = 20%.
Number of such number = 14.
I.E.
100% -------> 70 number.
X --------> 14.
(100x14) / 70 = 20%.
Rishav said:
9 years ago
Why you put 11 21 31and all?
Arjun said:
9 years ago
Please explain, what is unit digit?
Elly said:
9 years ago
@All.
This question has been tricky to understand but thanks to the various explanations. I've got it.
This question has been tricky to understand but thanks to the various explanations. I've got it.
Kamall Barik said:
9 years ago
Thanks for your shortcut @Syed.
Ramesh kannan said:
8 years ago
Very easy 100 ÷ 0 = 1.4285714286.
Next 1.4285714286 * 14 = 20.
Next 1.4285714286 * 14 = 20.
Panda said:
8 years ago
Why 1s of 12, 13,14...,18 is not calculated? Please explain.
Mustafa said:
8 years ago
Why 12, 13, 14, 15, 16, 17, 18 are not included?
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