A perfect is to be chosen from a class of 12 girls and 8 boys. What is the probability that the prefect is a girl?
2 answers:
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Make bottom number same
ok, so remember
(a-b)(a+b)=a²+b²
so
to get from (y-x) to (y²-x²), multiply 2nd fraction by (y+x)
so multiply 2nd fraction by (y+x)/(y+x)
=
=
ok, so remember
(a-b)(a+b)=a²+b²
so
to get from (y-x) to (y²-x²), multiply 2nd fraction by (y+x)
so multiply 2nd fraction by (y+x)/(y+x)