Q1
If P(E)=0.4, then P(not E) equals:
A0.6
B0.4
C1.4
D0
CBSEClass 10 (CBSE)MathematicsCh 14 · Topic 2
Probability of Complementary Events
Learning the relationship between the probability of an event and its complement.
Core concept
For example, if the probability of rain tomorrow is 0.3 (30%), the probability of no rain is 1 - 0.3 = 0.7 (70%), without needing any additional separate calculation. This complementary relationship is especially useful in problems where directly calculating the probability of 'not something happening' would be complex, but the probability of the event itself is straightforward to determine directly.
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• Complementary events: P(E) + P(not E) = 1.
• If P(E)=0.3, then P(not E) = 1-0.3 = 0.7.
• This shortcut avoids needing to separately calculate the complement's probability directly.
• Useful when calculating 'not happening' directly would be more complex than the event itself.