Answer:
The answer is 5050.
He uses Arithmetic Series.
Step-by-step explanation:
Arithmetic sequence = n/2 (a1 + an)
Where n is total Number of terms
a1 is the lowest number in the number of terms
and an is the highest number in the number of terms
n = 100
a1 = 1
an = 100
Sn = 100/2 (1 + 100)
= 50 (101)
Sn = 5050
-Senku