The name of the statistic that is a measure of the spread around the mean

Need help plz

Imagine a new pasture with grass growing on it. every day after the seeds have germinated, the number of blades of grass in the pasture triples. after 18 days, the entire pasture is completely covered in grass. how many days did it take for the pasture to be one-third covered in grass?

Rectangle leg this 11feet and perimeter of 38feet what is the width of the rectangle in feet

What are the equivalent ratios for 24/2= /3= /5.5=108/ = /15