6th Grade Math Textbook, Fundamentals

&KDSWHU 

3UDFWLFH   $FWLYLWLHV

Think

Fractional parts of a year are

represented as decimals:

6 months 0.5 year

9 months 0.75 year

2 years 6 months 2.5 years

Cell B2 is the box in column B,

row 2.

Cell C2 is the box in column C.

row 2.

A3*B3*C3 means that the

values in cells A3, B3, and C3

are multiplied using the formula

Iprt.

Find the simple interest, I, and the balance earned or due.

1.$800 at an annual rate of 8% for 9 months 2.$720 at an annual rate of 8.5% for 6 months

Find the annual interest rate, r.

3.$200 borrowed for 2 years, $24 in interest 4.$400 deposited for 9 months, $24 in interest

Find the time, t.

5.$350 at 8% per year, $84 in interest 6.$800 at 7% per year, $42 in interest

7.Discuss and Write Consider the interest on a savings account and the interest

on a car loan. How are they the same? How are they different?

You can find the amount of time that interest is paid or earned when you

know the principal, the annual rate of interest, and the interest amount.

Darrin borrowed $1100 at an interest rate of 6% per year. If he paid

interest of $297, for how many years did he take out the loan?

To find the timeof a loan or deposit, in years, use the interest formula

to solve for t.

Iprt

297 1100 • 6% • t

297 1100 • 0.06• t Write 6% as a decimal.

297 66.00t Multiply to simplify.

 Divide both sides by 66 to isolate t.

4.5 t

So Darrin took out the loan for a period of 4.5 years, or 4 years and 6 months.

Substitute $297 for I, $1100 for p,

and 6% for r.

66 t

66

297

66

The spreadsheet shows the balances for five different principal
amounts at an interest rate of 5% over a period of 3 years.

Cell D3 1000 • • 3  150

Cell E3  1000  150  1150

5

100

Lesson 7-13 for exercise sets.