Theory:

Multiplication:
When more than \(2\) numbers are multiplied, depending upon the number of negative numbers involved, the sign of the answer varies.
We know that,
\((-1) × (1) = -1\)
\((-1) × (-1) = +1\)
 
Now,
\((-1) × (-2) × (-3) = -6\)
\((-1) × (-2) × (-3) × (-4) = +24\)
\((-1) × (-2) × (-3) × (-4) × (-5) = -120\)
  
Inference:
When \(2\) negative numbers are multiplied, the result will be a positive number.
When \(3\) negative numbers are multiplied, the result will be a negative number.
When \(4\) negative numbers are multiplied, the result will be a positive number.
 
Conclusion:
From the above, we can conclude that,
Number of negative integers in multiplicationSign of the result 
Even\(+\)
odd\(-\)
 
Division:
Let's learn, how to deal with the division of more than \(2\) numbers, \(a,b,c\) are three numbers, \(a/b/c\) should be evaluated as \((a×c)/b\).
Example:
1.1/23=1×32=322.2/65=2×56=106
 \(a,b,c,d\) are four numbers, a/b/c/d should be evaluated as \((a×d)/(b×c)\)
Example:
1.5/23/6=5×63×2=3062.2/65/2=2×25×6=4303.2/46/2=2×26×4=424
Similar to multiplication, when more than \(2\) numbers are involved, depending upon the number of negative numbers involved, the sign of the answer varies.
Number of negative integers in division
Sign of the result 
Even\(+\)
odd\(-\)
Example:
1.5/22/8=5×82×2=4042.8/62/4=8×46×2=3212=32123.9/11/6=9×61×1=541=5414.1/21/2=1×21×2=22=15.122=1×22×1=1