MODE
AND
AND: P(A∩B)=P(A)×P(B)
ROUNDING
2DP
Decimal and % rounding
A INPUT
FRAC
A is converted to a decimal
A VALUE
3/10
For fraction use a/b
B INPUT
FRAC
B is converted to a decimal
B VALUE
1/4
For fraction use a/b
RULES (GCSE)
AND: multiply probabilities
OR (no overlap): add probabilities
Overlap: P(A)+P(B)-P(A∩B)
WORKING
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COMBINED P
READY
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MODE
AND
AND: P(A∩B)=P(A)×P(B)
ROUNDING
2DP
Decimal and %
A INPUT
FRAC
Convert to decimal
A VALUE
3/10
Fraction a/b
B INPUT
FRAC
Convert to decimal
B VALUE
1/4
Fraction a/b
WORKING
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COMBINED P
READY
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HOW TO USE
1) Pick MODE (AND/OR)
2) Enter P(A) and P(B)
3) Press SOLVE
4) Read decimal + %
AND (INDEPENDENT)
P(A ∩ B) = P(A) × P(B)
“A and B both happen”
Multiply decimals
OR (NO OVERLAP)
P(A ∪ B) = P(A) + P(B)
Only if they can’t both happen
Example: red OR blue
WORKED EXAMPLES
AND: 0.3 × 0.25 = 0.075
OR: 0.3 + 0.25 = 0.55
Percent = decimal × 100
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