Take a careful look at the following numbers:  
503 – 406 – 310 – 215 – ???  
Challenge:  
Figure out the last number so that they form a logical sequence.  

Answer:
Let’s break it down step by step:
Sequence given:  
503 → 406 → 310 → 215 → ???

Look at the differences between each pair:
- 503 − 406 = 97
- 406 − 310 = 96
- 310 − 215 = 95

So, each number is decreasing by 1 less than the previous difference.

Following the pattern, the next difference should be:
- 215 − 94 = 121

Final answer: 121

Bonus:
Can you find another way to find the same solution?
Show how two completely different thought paths lead to the same result.
Hint: look at the first digit from each number