Paper 6 May/June 2009 MATHEMATICH (9709/6) A Levels
لطفا برای اطمینان از عملکرد و تجربه بهتر از مرورگرهای مدرن و به روز مانند کروم یا فایرفاکس استفاده کنید.

A factory makes a large number of ropes with lengths either $3{\text{ }}m$ or $5{\text{ }}m$. There are four times as many ropes of length $3{\text{ }}m$ as there are ropes of length $5{\text{ }}m$.
a) One rope is chosen at random. Find the expectation and variance of its length.
b) Two ropes are chosen at random. Find the probability that they have different lengths.
Three ropes are chosen at random. Find the probability that their…