Answer:
20
Step-by-step explanation:
The average term in the series is the average of the first and last terms:
average term = (25 +101)/2 = 126/2 = 63
The sum of the series is the product of the average term and the number of terms:
Sn = n(average term)
1260 = 63n
1260/63 = n = 20
The number of terms in the series is 20.
