Question

practice

1. jonahs cell phone came with 64 gb of memory. he has used 15 gb. he then uses 5 mb of memory to record photos and videos from a trip. use the addition expression 64 + (-15) + (-5) to find how much memory is left on his phone.
2. stella walks down a flight of stairs to the basement. then she walks back up the stairs and up another flight of stairs to the second floor of her house. each flight of stairs represents a change of 12 feet in height. how far is stella above the ground?

Explanation:

Step1: Combine like - terms in the memory problem

We have the expression $64+(- 15)+(-5)$. First, we know that adding a negative is the same as subtracting. So, $64+(-15)+(-5)=64 - 15-5$. Then, we can combine the amounts of memory used: $15 + 5=20$. So the expression becomes $64-20$.
$64-(15 + 5)=64 - 20$

Step2: Calculate the remaining memory

$64-20 = 44$ GB.

Step3: Analyze the height problem

Stella walks down a flight of stairs (a change of - 12 feet), then walks up a flight of stairs (a change of + 12 feet) and then up another flight of stairs (a change of + 12 feet). The total change in height is $-12+12 + 12$.
$-12+12+12=( - 12+12)+12$

Step4: Calculate Stella's height above the ground

$-12 + 12=0$, and $0+12 = 12$ feet.

Answer:

1. 44 GB
2. 12 feet