99% Fail to Answer this Question ???

Study the following graph carefully and answer the questions that follow What is the over all percentage of failed boys over the period shown ?

In an examination paper of five questions, 5% of the candidates answered all of them and 5% answered none. Of the rest, 25% candidates answered only one question and 20% answered 4 questions. If 396 candidates answered either 2 questions or 3 questions, the number of candidates that appeared for the examination was

In an examination paper of five questions, 5% of the candidates answered all of them and 5% answered none. Of the rest, 25% candidates answered only one question and 20% answered 4 questions. If 396 candidates answered either 2 questions or 3 questions, the number of candidates that appeared for the examination was

Five question were asked in an examination. 5% of the total examinees answered all 5 questions and 5% of total examinees did not answered any question. 25% of the rest of the examinees answered only 1 question and 20% answered 4 questions. 24 (1)/( 2)% of the total examinees answered only 2 questions. If 200 examinees answered 3 questions, then find the total number of examinees.

About 99% of body Ca is present in bones and teeth as

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

Over 99% particular matter present in the exhaust from thermal power plant can be removed by :-

DDT on exposure to water decomposes according to first order kinetics. Half life = 10 years. How much time it will take for its decomposition to 99%?