Trina started with 250 dollars in her savings account. Every month, Trina spends 25 dollars from her savings account at the grocery store. Represent this situation with a table, a graph, and an equation.
Let’s start by representing this situation with a table. Start by finding the amount in the account after 0, 1, 2 and 3 months.
Time in months Number of dollars in the account
0
1
2
3
You got it!
Plot the points below on the coordinate plane to represent the amount in the account after 0, 1, 2, and 3 months.
Time in months Number of dollars in the account
0 250
1 225
2 200
3 175
Nice!
We can connect the points you just graphed with a line. To find the equation that represents this linear function, you’ll need the rate of change and the initial amount in the account. Start by finding the rate of change. In other words, by how much does the amount in the savings account change each month?
t
y
0
1
2
3
4
5
0
25
50
75
100
125
150
175
200
225
250
Time in months
Number of dollars in the account
Rate of change:
You got it!
Now, record the initial amount. What was the initial amount in the savings account?
t
y
0
1
2
3
4
5
0
25
50
75
100
125
150
175
200
225
250
Time in months
Number of dollars in the account
Rate of change: -25
Initial amount:
Initial amount: 250 dollars
Now, we can find the equation for the amount in Trina's savings account after a certain number of months. The equation for a linear function is: y = mx + b, where y represents the amount in the account, x represents the number of months, m represents the rate of change, and b represents the initial amount.
Using the rate of change of -25 dollars and the initial amount of 250 dollars, the equation for this situation is:
y = -25x + 250
This equation represents the amount in Trina's savings account after a certain number of months.