Question

To decrease an amount by 85% what single multiplier would i need to use?

Answer 1

You are asking about what number must you multiply another random number by to make that random number decrease by 85% of that random number, right?

If the above is correct, then the number is 0.15
because 100% - 85% = 15% and 15% = 15 / 100
= 0.15