1. A1=10, A2=20, A3=30...A10=100
2. C1=5
3. In column B I want to multiply each number in column A by C1
4. In B1 I enter "=A1*$C$1"
5. In B1 "30" appears as expected. But when I click and drag the fill handle to B2-B10, "30" also appears in all those cells as if I had copied the formula without conditionally formatting C1.

This has worked as it should in the past, so I am not sure what is wrong. I am using Excel 2016 in Windows 10. I tried the same thing in another workbook without luck.

Anyone able to tell me what might be wrong? Thanks!