Colin invests £1200 into his bank account. he receives 3% per year simple interest. how much will colin have after 4 years? give your answer to the nearest penny where appropriate.

What is the number 321,000,000 in scientific notation? also what is the number? ?

How do i make someone brainliest? (if you answer me, i might be able to make you brainliest! )

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?