The formula for compound interest is:

Given data:

a. After ten years, that is t = 10 years, the amount in the account will be

b. After twenty years, that is t = 20 years, the amount in the account will be:

c. The time it takes for Harry's initial account value to double will be:

Therefore, the time it takes Harry's initial account to double is approximately 11 years
To compare, think of the ratios as a fraction. so it is 32 slices per $7.99.
You can also say $7.99 per 32 slices.
so it can be ̲7̲.̲9̲9̲ ̲ or the other way around.
32
To find the unit price, or the price of 1 item, you have to divide the price by the amount.
So 7.99 divided by 32 is <span>0.249687, but we don't have thousandths of a cent, so we round to the hundredth.
$0.25 is the unit price, or the price of 1 toast, rounded to the nearest cent.
So let's try another one, this time we have 2 different rates, and we will compare them.
So let's say we are buying cheese. Store A sells 12 blocks of cheese for $14.99, and Store B sells 20 blocks for $23.99.
So first we have to find the unit rate for each.
Store A Store B
14.99 per 12 23.99 per 20
</span> ̲1̲4̲.̲9̲9̲ ̲ ̲2̲3̲.̲9̲9̲ ̲<span>
12 20
14.99 / 12 is </span>1.24916 23.99 / 20 is <span>1.1995</span>
<span>$1.25, if rounded to the cent. $1.20, if rounded to the cent
</span>1 block is $1.25 in Store A. 1 block is $1.20 in Store B
Store B sells for cheaper.
Hope that helps.
1.25 is the slope 5/4 rise over run