If we have four positive numbers a, b, c and d, there are six ways to multiply............What is the remaining product?

Question

If we have four positive numbers a, b, c and d, there are six ways to multiply the pairs i.e. a*b, a*c, a*d, b*d and c*d. If we tell you the result of five of them without telling you which one is the product of which pair as 2, 3, 4, 5 and 6.

What is the remaining product?

Answer 1

9

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Let's assume
a*b=2, a*c=3, a*d=4, b*c=5, b*d=6
c*d=?
from equations above we have a=2/b, c=3/a=3/2/b=3b/2 & d=6/b,
then
c*d=3b/2*6/b=9