Increase percentage formula

[Guest]

In a1 I have an increase amount of 3%

in B1 I have the toal I pay this month.

In C1, if I want to show last months amount times the increase how do I
write this formula? The only way I can think of is only showing 3% of last
months total.

By the way I am hoping to keep this format because I want to be able to
change the amount in A1.

Thanks

 

[Guest]

in C1 enter =(1+A1)*B1 if C1 is the new pay and B1 is the old pay.

in C1 enter =B1/(1+A1) if C1 is the old pay and B1 is the new pay.

Regards,