Did You Know This? 99% Fail

Which of the following device is used to remove over 99% particulate matter present in the exhaust from a thermal power plant?

In an examiniation 55% of the students failed in chemistry, 47% failed in physics and 23% failed in both, find the pass percentage of the class.

In a college, 30% students fail in physics, 25% fail in Mathematics and 10% in both. One student is choosen at random. The probability that she fails in physics, if she has failed in Mathematics is

The insecticide containing 99% gamma - isomer of benzene hexachloride is known as