You start with a number. double it. square the answer. you get 400. what number did you start with?

Ill mark the brainliest if you me with the these three questions 7,8,9

What is the simplified form of (3.25x10^3)(7.8x10^6) written in scientific notation?

Meghan has created a diagram of her city with her house, school, store, and gym identified. a. how far is it from the gym to the store? b. meghan also wants to walk to get some exercise, rather than going to the gym. she decides to walk along arc ab. how far will she walk? round to 3 decimal places.