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Dear PKN, I dont see where Davidtutor says "160 #customers bought chocolate pies" (that would be wrong).
His explanation is correct in my opinion. The other explanations of the other users are wrong (even if they come to the same answer D).[/quote]
Hi
gioacchinorossiniExtended explanation:-2 overlapping sets can always be broken into the same 4 categories (both, only A, only B, neither).
This is a Precise approach.
total number of pies= 200
(both chocolate and cocount) = 80neither = 0 as all customers bought at least one pie
so (only chocolate) + (only cococunt) = total - (both) - (neither) = 200 - 80 - 0 = 120
question - how much is
(only chocolate) + (both chocolate and coconut)?
Since we know that
(only chocolate) + (only coconut) = 120,
----(1) all we need to is the value of (only coconut).
(1) then these 40 must have bought a cococunt pie meaning that (only coconut) = 40. Exactly what we need!
Now, from eq(1), Only chocoloate=120-40=80
Therefore, (only chocolate) + (both chocolate and coconut)=80+80=
160Sufficient.
(2) gives us (only coconut) + (both). Since we know that (both) = 80, we can calculate (only coconut).
So, Only Coconut=120-80=40
Now, from eq(1), Only chocoloate=120-40=80
Therefore, (only chocolate) + (both chocolate and coconut)=80+80=
160Sufficient.
Note:- In DS questions, exact computation is not required. Mr. David did the same thru reasoning, final answer(numerical value) is not required , only data sufficiency is checked.
_________________
Regards,
PKN
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