Question

daily word problems wednesday-week 8
maria is proud of her seashell collection. she has 9 boxes of seashells. the first box has 1 seashell in it. the second has 2 seashells in it, the third has 3, and so on. how many seashells does maria have in all 9 boxes?
name:
work space:
answer:
______ seashells in all

Explanation:

Step1: Identify the sequence

The number of seashells in each box is 1,2,...,9 (arithmetic sequence).

Step2: Use sum formula

Sum of first $n$ integers: $\frac{n(n+1)}{2}$, $n=9$.

Step3: Calculate the sum

$\frac{9×10}{2}=45$.

Answer:

45