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 7 of 11.
Soujanya said:
9 years ago
What if larger numbers are given?
Eg: 1 to 10000. We cannot count manually all the numbers right, Is there any shortcut?
Eg: 1 to 10000. We cannot count manually all the numbers right, Is there any shortcut?
Honey said:
9 years ago
Thanks for your clear solution @Tabi.
Gain.... said:
9 years ago
But they asking 1 or 9 (if they asking instead of this 1 and 9). What will be the answer?
Amit Das said:
9 years ago
Why not 12, 13, 14, . , 18? All have 1 in them! It is told 1 OR 9. Not 1 AND 9?
Ajinkya said:
9 years ago
11, 19 is a prime number. So why they are included in squares?
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?
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