An industrial filter removes 90% of the particulate matter from the exhaust gases of a furnace. How many filters must the gas pass through in order to remove 99.9% of the particles before releasing the gases to the outside air? (Exponential decay/growth)

What are the options

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.