Here's the last of the problems that i'm not sure how to tackle.

A group of students where studying how fast a plant was growing. Once a day they measured the plant. These was the results:

Day--- length (cm)

0 -----0,5

1 -----0,8

2 -----1,3

3 -----2,1

4 -----3,3

5 -----5,2

6 -----8,1

7 -----13,4

The students created an equation from this information: y=0,5*1,6^X

X is time in days. Y is the height of the plant.

How did the students work out 1,6 from this information?