1962 IMO Problems/Problem 1
Problem
Find the smallest natural number 
which has the following properties:
(a) Its decimal representation has 6 as the last digit.
(b) If the last digit 6 is erased and placed in front of the remaining digits, the resulting number is four times as large as the original number .
Video Solution
https://youtu.be/9y5UUNIhUfU?si=PzXbNokxOXCRxYBh [Video Solution by little-fermat]
Solution 1
As the new number starts with a 
and the old number is 
of the new number, the old number must start with a 
.
As the new number now starts with 
, the old number must start with 
.
We continue in this way until the process terminates with the new number 
and the old number 
.
Solution 2
Let the original number = 
, where is a 5 digit number.
Then we have 
.
=> 
.
=> 
.
=> 
.
=> The original number = 
.
See Also
| 1962 IMO (Problems) • Resources | ||
| Preceded by First Question |
1 • 2 • 3 • 4 • 5 • 6 | Followed by Problem 2 |
| All IMO Problems and Solutions | ||
