Question

Eighteen integers are multiplied together. What will be the sign of their product, if:​
(iv)All are negative?​

Answer 1

The product of an odd number of negative integers is always negative.​
The product of an even number of negative integers is always positive.​
Here we have $18$ integers that are multiplied together and all are negative integers.​
Since the number of negative integers is even $\left(18\right)$, their product would always be a positive integer.​
$\therefore$ By multiplying $18$ negative integers, the sign of their product will be positive.​