You have to pay someone 25 rubles. He has three conditions:
- He should be paid exactly 25 rubles, neither less nor more.
- Only 1 ruble notes, 3 ruble notes and 5 ruble notes are acceptable to him. No other kind of notes is acceptable.
- He should be paid using exactly 10 notes.
Will it be possible to pay him ?
Difficulty rating:
Easy. 3.5/10
Solution:
When you add 2 odd numbers, the result is always even. Example: 3+17= 20, 1+5 = 6
So, if there are 2x odd numbers, where x is a positive integer, the sum of these 2x numbers will also be even.
If x = 5 then it would mean that there are 10 odd numbers and the sum of these 10 odd numbers will have to be even.
Therefore, since the person wishes to be paid with exactly 10 notes and since all these 10 notes would each have an odd value, it will not be possible to sum these 10 notes to 25, which is an odd number.