A group of students took a test which consisted of 3 questions. We know that 90 % answered the first question correctly, 80 % answered the second question correctly and 70 % answered the third question correctly. What is the smallest possible percentage of students who answered all three questions correctly?
A 30 % B 35 % C 40 % D 50 % E 70 %
C
There are a group of 10 % who failed to answer correctly the first question, 20 % for the second and 30 % for the third. The number who failed on one or more questions will be largest if these groups do not overlap; and in that case they will form 60 % of the whole group. So the smallest possible percentage of students who got all correct is 40 %.
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