How to multiply entire colume with constant:

For example I have colume A


21
26
28
33
77


I wish to multiple all of colume A with 7 and put product result in colume B

21 147
26 182
28 196
33 231
77 539

how do I insert single formula vulue in colume B at one time during edit?
(by selecting all the cells in colume B)?

Thank you.