the probability the marble will be blue is

½

opsi C.

Diketahui:

There are red, blue, and black marbles in a bag. The probability of pulling out a red marble is ⅖. The probability of pulling out a black marble is 1/10. One marble is pulled out at random.

Ditanya:

What is the probability the marble will be blue?

Pembahasan :

misal total jumlah n(S) = x

n(red) + n(black) + n(blue) = x

P(red) = n(red) / n(S)

⅖ = n(red) / x

n(red) = ⅖x

P(black) = n(black) / n(S)

1/10 = n(black) / x

n(black) = 1/10 x

n(red) + n(black) + n(blue) = x

⅖x + 1/10 x + n(blue) = x

n(blue) = x - ⅖x - 1/10 x

= (10/10 - 4/10 - 1/10)x

= 5/10 x

= ½x

P(blue) = n(blue) / n(S)

= ½x / x

= ½