Exercise 29 Page 400

In order to determine which account has the greatest interest rate, we need to calcualte the interest rate for each account, then compare them. First, let's take a look at the given table.

	Principal	Interest Earned
Account A	$ 90.00	$ 4.00
Account B	$ 120.00	$ 5.50
Account C	$ 100.00	$ 4.80

We can calculate the interest rate for each account if we divide the interest earned by the principal of the account. To make the comparisons easier, we will write the result as a percent. Remember that to write a number as a percent, it is easier if the number is in decimal form first. Let's start with Account A. Interest Earned/Principal ⇒ $ 4/$ 90Notice that the fraction 490 cannot be written as ab, where a is an integer and b is a power of 10. This means that the decimal form of the fraction will not terminate, so instead we need to use long division to divide 4 by 90. Let's do it!

We can see that the quotient begins to repeat after the third step. We will stop our division here and draw a line over the repeating digit in the quotient. 4/90=0.04 To convert this decimal to a percent, we simply need to multiply it by 100 %. 0.04* 100 % = 4.4 % We found that the interest rate of Account A is 4.4 %. Next, we will do the same for Account B. Let's take a look at the next fraction. $ 5.50/$ 120=55/1200 This fraction is also non-terminating, so let's use long division to divide 55 by 1200.

As we can see, the remainder repeats after the sixth step. Let's multiply the repeating decimal by 100 % to find the interest rate of the second account. 0.04583* 100 % = 4.583 % Now let's consider Account C. From the table, we can see that the principal amount of $ 100 earned $ 4.80 in interest. Since a percent can be expressed as a fraction over 100, we do not need to make any calculations. $ 4.80/$ 100=4.8 % Finally, we can see that Account C has the greatest interest rate.