a las 8 a. m un termómetro marcaba -3 grados centígrados 4 horas después la temperatura subió a 5 grados centígrados y 7 horas después bajó 8 grados centígrados Qué temperatura marca un termómetro a las 7 pm​

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?