In a class of 25 students, 15 of them have a cat, 16 of them have a dog and 3 of them have neither.
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Answer:
25150
Step-by-step explanation:
First, we have to see that this is an arithmetic sequence... since to get the next element we add 5 to it. (a geometric sequence would be a multiplication, not an addition)
So, we have a, the first term (a = 4), and we have the difference between each term (d = 5), and we want to find the SUM of the first 100 terms.
To do this without spending hours writing them down, we can use this formula:
If we plug in our values, we have:
S = 50 * (8 + 495) = 50 * 503 = 25150