Writing addition equations with rational numbers to represent situations
About this video
A buoy measures water level relative to average sea level. The water starts at x meters, rises 1.8 meters, and ends at -3.4 meters, so the equation is x + 1.8 = -3.4. The narrator explains that -3.4 means below average sea level and suggests clearer wording for the question.
You'll be able to
- write an addition equation with decimals and negative numbers for a situation.
- interpret a negative water level relative to average sea level.
Key words
- buoy
- A floating marker in the water; this one records the water level.
- average sea level
- The usual height of the sea, used here as zero.
- low tide
- The time when the sea is at its lowest level.
Transcript
- [Instructor] We're told A buoy records the water level relative to the average sea level. The water level is represented by x meters. After the water level rises by 1.8 meters, the water level is negative 3.4 meters. Write an equation using x to represent this situation.
All right, pause this video and have a go at that. Okay, so at least the way they've written it, it says the water level is represented by x meters. After the water level rises by 1.8, the water level... So I think the way they're saying is the water level is originally x meters, so originally x meters, and then what is it going to be after the one point, or after the 1.8 meter rise?
It's now negative 3.4 meters. So if it's starting at x, x meters, and then it rises by 1.8 meters, and then after rising by 1.8 meters, it gets to negative 3.4 meters, then this would be my equation. Now, some of you might be wondering, "What does negative 3.4 meters mean?"
Well, that means that the current water level is 3.4 meters below the average sea level, so we're probably at low tide at that point. So this would be my equation. If I were tweaking this, I would make this question a little bit more precise. I would say the water level started at x meters. Started.
Started, or the starting water, let me put it this way. The starting, starting water level is represented by x meters. After the water level rises by 1.8 meters, the maybe, the water level is negative 3.4. Yeah. Then I like this and I like my equation.
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