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Mathematics Elective Course 2 in Senior Two
Touch two balls randomly from two bags A and B, and each ball may appear.

1 white 1 yellow, 2 white, 2 yellow

The probability of bag A getting 1 white 1 yellow 2 white 2 yellow is

P( 1 white 1 yellow) = C3 (1) * C2 (1)/C5 (2) = 3/5.

P(2 white) =C3(2)/C5(2)=3/ 10.

P(2 yellow) = C2 (2)/C5 (2) =110

The probability of bag B getting 1 white 1 yellow 2 white 2 yellow is

P( 1 white 1 yellow) = C5 (1) * C3 (1)/c8 (2) =15/28.

P(2 white) =C5(2)/C8(2)=5/ 14

P(2 yellow) =C3(2)/C8(2)=3/28

The absolute value of the difference between the number of yellow balls and the number of white balls is x: 0, 2, 4.

p(x = 0)= 3/5 * 15/28+3/ 10 * 3/28+ 1/ 10 * 5/ 14 = 109/208

P(x=2)= 138/280

P(x=4)=33/280

Probability distribution of x

X 0 2 4

p 109/280 138/280 33/280

Expected value of mathematics

EX = 0x 109/280+2x 138/280+4x 33/280 = 5 1/35