how to make multiplication in Kernel Linux?

everyone I'm interested how can I make multiplication the best way in Linux Kernel, I know that in Kernel (version 2.4.18) I can't just multiply by 0.49 (for example) but if I need inferior limit of x * 0.49, what am I supposed to do, thanks in a开发者_运维技巧dvance P.S. I can't do (x/100)*49 cause I don't receive an accurate result

Reverse the operations. Multiply by 49, then divide by 100.