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:
103 comments Page 10 of 11.
Daniel said:
1 decade ago
The question doesn't specify that the digits 1 or 9 must be the last digits, so clearly all the number in the teens, would qualitfy as nubers between 1 and 70 that have the digit 1 OR 9.
Naga said:
1 decade ago
I con't understad this problem
Joape said:
1 decade ago
It does not count 10, 12, 13, 14, 15, 16, 17, 18.
and they did not state about the square in the question.
and they did not state about the square in the question.
Uttam said:
1 decade ago
Inside the 10 there are 2 digits which ends with 1 and 9.
Number 70 consists 7 tens.
So total no of digits that end with 1 and 9 in 70 are,
7*2=14.
So percentage= (14/70) *100=20.
Number 70 consists 7 tens.
So total no of digits that end with 1 and 9 in 70 are,
7*2=14.
So percentage= (14/70) *100=20.
Gopal said:
1 decade ago
@pankaj.
It is wrong method unit digit means endshould be 1 or 9.
And 10 will be end in 0 so 10 is not include.
It is wrong method unit digit means endshould be 1 or 9.
And 10 will be end in 0 so 10 is not include.
PANKAJ said:
1 decade ago
@ ROSS
The no 10 after squaring it does not end with 1.......
if u square to 1,11,19,21 it ends with 1
Squaring 10 = 10 x 10 = 100 it ends with 0
Squaring 11 = 11 x 11 = 121 it ends with 1
I think u got it.
The no 10 after squaring it does not end with 1.......
if u square to 1,11,19,21 it ends with 1
Squaring 10 = 10 x 10 = 100 it ends with 0
Squaring 11 = 11 x 11 = 121 it ends with 1
I think u got it.
Pankaj said:
1 decade ago
Very good priya.
Ross said:
1 decade ago
I see that number 10 is not included into consideration even though it has 1 in its digit unit, why?
Saranya said:
1 decade ago
Thank you for your short cut syed.
Priya P. said:
1 decade ago
@chandrakala
Its not end in 1 digit, its end with digit 1
as (1)^2=1
(9)^2=81 ;8(1)
got it..
Its not end in 1 digit, its end with digit 1
as (1)^2=1
(9)^2=81 ;8(1)
got it..
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