Check the attachment.

you can easily see this by drawing ven diagrams, but I'll try to explain it in words.

You have 4 options
- buy p and not q
- buy p and buy q
- not p and buy q
- not p and not q

knowing any 3 will allow you to solve the 4th

so... (1) says p and not q --> insuff

(2) says buy q -- so that constitutes buy p and not q and buy p and buy q --> still insuff

(combined) we have 3 of the above options so we can solve for unknown

... you don't need to ACTUALLY solve, just need to know that you COULD solve to show sufficiency

hope that helps

Xbond wrote:Hi there,

Could you explain in the simplest this concept and how to resolve it


A manufacturer conducted a survey to determine how many people buy products P and Q.
What fraction of the people surveyed said that they buy neither product P nor product Q ?

(1) 1/3 of the people surveyed said that they buy product P but not product Q
(2) 1/2 of the people surveyed said that they buy product Q

Rephrase :

P + Q - Both + Neither = 100

1. Gives (P - Both) info - No info about Q. insufficient
2. Gives Q info - No info of P & Both. Not sufficient

1&2 -> We have (P-B) & Q, we can find Neither.

HTH.