Answer:
24 terms
Step-by-step explanation:
The sum of an arithmetic sequence is the average of the first and last terms, multiplied by the number of terms. The last term is given by ...
an = a1 + (n-1)d
We have a sequence with first term a1 = 2 and common difference d = 2. So the last term is ...
an = 2+ 2(n -1) = 2n
Then the average of first and last terms times the number of terms is ...
Sn = 600 = n(2 + 2n)/2 = n(n+1) . . . . . . close to n²
We can solve the quadratic in n, or we can estimate the value of n as the integer just below the square root of 600.
√600 ≈ 24.5
so we believe n = 24.
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Check
S24 = 24·25 = 600 . . . . . . as required.
