standard_description: Use numbers expressed in the form of a single digit times an integer power of 10 to estimate very large or very small quantities, and to express how many times as much one is than the other. For example, estimate the population of the United States as 3 × 108 and the population of the world as 7 × 109, and determine that the world population is more than 20 times larger.
problem_activity: Task
Decide which of the following equations best represents each situation.
| $$x + 2= 10$$ | $$x=10+2$$ | $$2\cdot10=x$$ |
|---------------|------------|----------------|
|  $$x+10=2$$   | $$10x=2$$  |   $$2x=10$$    |
After Lou poured 2 liters of water into a large jug, the jug contained 10 liters of water. How many liters were in the jug to start?
Clara ran 10 miles, which was twice as far as Nina ran. How far did Nina run?


aligns: no