Pls help or i will fail

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?

Television viewing reached a new high when the global information and measurement company reported a mean daily viewing time of 8.35 hours per household. use a normal probability distribution with a standard deviation of 2.5 hours to answer the following questions about daily television viewing per household. a. what is the probability that a household views television between 4 and 10 hours a day? (to 4 decimals) b. how many hours of television viewing must a household have in order to be in the top 7% of all television viewing household? (to 2 decimals) c. what is the probability that a household views television more than 4 hours a day? (to 4 decimals)

Marcus needs to bike at least 80 miles this week for his training. if he has already biked 25 miles this week, then how many miles should he bike on each of the 5 remaining days this week ?