another probability q. (1 Viewer)

[speed2]

When Medel crossed a tall strain of pea with a dwarf strain of pea, he found that 3/4 of the offspring were tall and 1/4 were dwarf; suppose 5 such offspring were selected at random. find the probability that at least 3 of these offspring were tall.

its from the '91 HSC. answer is 459/512.

thx guys

 

[haboozin]

When Medel crossed a tall strain of pea with a dwarf strain of pea, he found that 3/4 of the offspring were tall and 1/4 were dwarf; suppose 5 such offspring were selected at random. find the probability that at least 3 of these offspring were tall.

its from the '91 HSC. answer is 459/512.

thx guys

bionomial probability

5c3x3/4^3x1/4^2 + 5c4x3/4^4x1/4 + 3/4^5

 

[HayleeKate]

P(at least 3 tall)= P(3tall) + P(4tall) = P(5 tall)
= 5C3.(3/4)^3(1/4)2 + 5C4.(3/4)^4.(1/4)^1 + 5C5.(3/4)^5(1/4)^0
=10.27/1024 + 5.81/1024 + 243/1024
=459/512