Final answer:
The probability of not having twins can be calculated by subtracting the probability of having twins from 1. The probability of not having twins is 0.989.
Step-by-step explanation:
The probability of not having twins can be calculated by subtracting the probability of having twins from 1.
Probability of not having twins = 1 - Probability of having twins
Probability of not having twins = 1 - 0.011 = 0.989
Therefore, the probability of not having twins is 0.989.