If a*b denotes the greatest common divisor of a and b, then ((16*20)*(18*24)) = ?  Options.
A) 24	B) 12	C) 6	D) 4	E) 2

Rationale: the greatest common divisor of 16 and 20 is 4 . hence 16 * 20 = 4 ( note that * here denotes the function not multiplication ) . the greatest common divisor of 18 and 24 is 6 . hence 18 * 24 = 6 . hence ( ( 16 * 20 ) * ( 18 * 24 ) ) = 4 * 6 . the greatest common divisor of 4 and 6 is 2 . answer ; e .
Answer: E