Question

Find the sum of all positive integers, from 5 to 1555 inclusive, that are divisible by 5

Answer 1

a = 5
d = 5
nth term = a + (n-1)d
1555 = 5 + (n-1)5
1550/5 = n-1
310 = n-1
n = 311

Sum
$\frac{n}{2} (2a + (n - 1)d) \\ \\ \frac{ 311}{2} (10 + 1550) \\ \frac{311}{2} \times 1560 \\ 311 \times 780 \\ 242580$

Answer 2

done Dana done. gwgff