Which prefix means 1/10 of a unit in the metric system?

a. deci b. centi c. hecto d. milli

Can someone me out here number 4 plz

Is triangle jkl congruent to triangle rst? if so, what is the scale factor?

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?