Ascience teacher needs to choose 4 students from a class of 20 to go to the library to do some research. how many different groups can he select?

In the image, point a marks the center of the circle. which two lengths must form a ratio of 1 : 2? (options are in the images since thought they were harmful phrases)

What is the best approximation for the area of a circle with a radius of 4 m ? use 3.14 to approximate pi

How to simply and write the answer n a whole number