Step 1: The sum is 1+2+⋯+49+50+49+⋯+3+2+1.
This equals the sum from 1 to 50 plus the sum from 1 to 49:
∑k=150k+∑k=149k
Step 2: Use the formula for the sum of the first n natural numbers:
∑k=1nk=2n(n+1)
Step 3: Compute ∑k=150k:
250×51=22550=1275
Step 4: Compute ∑k=149k:
249×50=22450=1225
Step 5: Add the results:
1275+1225=2500
2500