udaymathapati wrote:
If r, s, and w are positive numbers such that w = 60r + 80s and r + s = 1, is w < 70?
(1) r > 0.5
(2) r > s
Sol: Given r,s and w are positive nos and w=60r+80s and r+s=1
We need to know whether w<70 or not
Given r+s=1 so 60r+60s=60---> The given expression for w = 60r+60s+20s or w=60+20s
The question becomes is 60+20s<70 or s<1/2
St 1: If r>0.5 then s<0.5 because r+s=1. Sufficient
St 2: r>s. Okay it is given that r+s=1 so as r increases, s decreases and r=s=0.5. Since r>s therefore r has to greater than 0.5 and hence s < 0.5
Ans is D
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65% (01:58) correct 
