✔ Subtract probability from one to find complement.
Q2. Probability of rain is 2/5. Chance no rain?
✔ One minus two-fifths equals three-fifths.
Q3. Sum of P(E) and P(not E)?
✔ Fundamental rule states sum is always one.
Show transcript
[Slide 1] What is a Complement?
Imagine flipping a coin. Either heads comes up or it does not. These two outcomes cover all possibilities together.
[Slide 2] The Complementary Rule
To find the chance something won't happen, just subtract its chance from one. This rule saves time in calculations.
[Slide 3] Dice Roll Example
If you roll a die, the chance of a six is one out of six. To find the chance of not rolling a six, subtract that from one.
[Slide 4] Watch Out for Errors
Students often forget that probabilities must sum to one. Do not assume the complement is just the opposite number without calculation.
[Slide 5] Key Takeaways
Remember that an event and its complement make a whole. Master this rule to solve probability questions faster in exams.