Plz tell me ans fast

Two sides of a triangle mesure 20cm and 30cm. what is the measure of the third side

The last time i bought this product , it cost $20.00 but it looks like it cost 29. 60 today? what is the increase

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?