Which interest formula do banks normally use - simple interest or compound interest?

If you are offered a 50% interest rate for your savings account (deposit) - what will you do?

I want to open a savings account. The bank offers me a 10% interest rate. I deposit 1000$ for 2 (!) years. Using a compound interest, calculate how much money you will have by the end of your 2nd year.

I want to invest in a company. They promised me high returns but I don't see how they are going to make so much money. Should I invest?

What's the formula of compound interest?

What's the formula of simple interest?

I want to take a loan - 500$. The bank offered a 7% loan, but I have to return money in 1 year. How much money will I return in total?

What's the difference between simple interest and compound interest?

What is interest rate?

In which situations you may use simple or compound interest?