<span>The number 123,000,000,000 in scientific notation is written as : 1.23 * 10 to the eleventh power.
Thats an example to help you out ;)
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Have you got your answer yet?
So in 30 min will hike 2 1/4 miles =9 of those 1/4 miles therefore in 10 min will hike 9/3 =3 of those 1/4 miles = 3/4 of a mile
3/4 mile in 10 min;
(3/4)• 4 = 3 miles in 40 min;
6 miles in 80 min;
9 miles in 120 min;
12 miles in 160 min;
15 miles in 200 min;
18 miles in 240 min or 4 hours
We have sequence equation 
.
In this case n is a natural number (1, 2, 3, ...).
So start inserting and computing value of 
given that you know the value of n and a.
(first term)
Hope this helps.
