In this lesson, you will learn how to determine the solution to an exponential equation using tables and/or graphs.

Table Method

Celeste deposited $10,000 into a savings account that pays 2.8% compounded monthly. The equation below represents the amount of money, A, Celeste will have in t years.

the formula A equals 10000 times the quantity 1 + .028/12) raised to the 12t

Celeste wants to know how many years will it take her to earn $1,000 in interest.

To solve this using a table, you should understand that Y1 represents the amount of money that will be in the savings account after x years.
Step 1: Enter equation into [Y=].

graphing calculator screen showing Y1equals 10000 times the quantity 1 + .028/12) raised to the 12X

Step 2: Go to table.
How long will it take Celeste to earn $1,000?

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Check Your Answer

Since she began with $10,000 in her account, it will take her between 3 and 4 years to earn $1,000.

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graphing calculator screen showing a table of values for X and Y1 from X =0 to X= 6

Step 3: To access TABLE SETUP menu, choose
[2nd][Window]

To get a more precise answer, change the table interval to 0.1

Why was TblStart set to 3?

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Check Your Answer

Since we know that it will take her between 3 and 4 years to earn a $1,000, starting the table at 3 will reduce the amount of scrolling needed to find the solution.

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graphing calculator screen showing TABLE SETUP with TblStart at 3 and ∆Tbl=0.1 Indpnt and Depend are both set at Auto

Step 4: Go back to the table.

Based on this table, how many years will it take Celeste to earn $1,000?

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Check Your Answer

It will take at least 3.5 years to earn $1000.

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