请教PREP数学题

tigerflying

152. The probability of red: P(r)=r/(b+w+r), and the white P(w)=w/(b+w+r), so if (r)>(w), then r>w.

(1).r/b+w>w/b+r,-->(r-w)(1-1/b)<0 , because b is positive integer, so (r-w)<0.

(2) b-w>r  --->b>w+r, could not get the result r>w.

so the answer should be A

140.From the information, we could get V94=V93(1+x%), and V95=V94(1+y%), so V95=V93(1+x%)(1+y%)=V93(1+x+y+xy%)%, so (2) i enough.