Question

Dry cleaners use a cleaning fluid that is purified by evapouration and condensation after each cleaning cycle. Every time the fluid is purified,2.1% of it is lost. The fluid has to be topped up when half the original fluid remains. After how many cycles will the fluid need to be topped up?

Answer 1

logarithmic type of question.

Answer 2

0.5 = (1-0.021)^n

ln(0.5) = n ln(0.979)

n = ? answer = about 33.