3 years ago, the residents of Planet X found a black hole leading to another galaxy. Since then, they have been leaving Planet X at a rate of 120 residents per year.
3yrs. * 120res./yr. = 360 left.
To find the total number of residents who have left Planet X over the course of 3 years, you need to multiply the rate of leaving (120 residents per year) by the number of years (3).
You can use the formula:
Total number of residents leaving = Rate of leaving × Number of years
Plugging in the values:
Total number of residents leaving = 120 residents/year × 3 years
Simplifying this equation, you get:
Total number of residents leaving = 360 residents
Therefore, a total of 360 residents have left Planet X in the past 3 years.