Year 12s: what will be the first way you research your future options? >>

S1 Edexcel question help please!

I'd really appreciate it if you could look at this paper please
http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/January%202009/6683_01_que_20090119.pdf

A quick question with question 3e,

the answer is...

0.3x0.1 + 0.1x0.3 + 0.2x0.1 + 0.1x0.2 + 0.1x0.1 + 0.2x0.2 = 0.15

However, why isn't the (0.2x0.2) and (0.1x0.1) done twice like the others?

Hope that makes sense

Would really appreciate the help

thank you!! :biggrin:

Reply 1

Groat

Getting 3 and 3, and 2 and 2 can only be achieved one way. The others can be achieved two ways, so the probability is doubled: for example, to get 1 and 3, you could first get 1, then get 3; or get 3, then get 1.

I hope that makes sense!