Usually in GMAT problem,arithmetic operations are represented by some symbols.WE need to solve the equation.
Here a*b=a+b-ab[* refer to that symbol]
Option1:
a*b=a+b-ab
b*a=b+a-ba=a+b-ab
Both are same
Option2:
a*0=a+0-0=a
Bothe are same
Option 3:
Now take LHS
(a*b)*c
(a*b)=a+b-ab
(a+b-ab)*c=a+b-ab+c-(a+b-ab)c
=a+b+c-ab-(ac+bc-abc)
=a+b+c-ab-ac-bc+abc
Now take RHS
a*(b*c)
(b*c)=b+c-bc
a*(b+c-bc)=a+b+c-bc-a(b+c-bc)
=a+b+c-ab-ac-bc+abc
LHS=RHS.
Option 3 is also correct.
Hope this clarify....
GMATPrep 1 - question
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Source: Beat The GMAT — Problem Solving |
