In a group of 34 students, 11 study both Art and Biology. 15 study Biology but not Art.
4 study neither subject.
Given that a randomly selected student studies Art, what is the probability the student studies Art and Biology?

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?

The product of sin 30 degrees and sin 60 degrees is same as the product of

The high temp today was 62°. when nighttime comes, the temp will drop 40°. by 4am the temp will drop an additional 40°. what is the temp at 4am?