Begin by subtracting 1/8 from both sides to get

and get a common denominator of 8 on the right:

. Now simplify and cross-multiply: 39x = -16 andx = -16/39
Okay. The formula for simple interest is prt. You multiply the principal (initial amount) by the rate (percentage) by the time (months or years). $1,800 is the principal and 6.5% is the percentage rate. 1,800 * 6.5% (0.065) is 117. You earn $117 in interest annually. The time period is 30 months. There are 12 months in 1 year. Divide the amount of months by 12 to put it in a decimal. 30/12 is 2.5. Now, multiply 117 by 2.5 to find the total amount of interest earned. 117 * 2.5 is 292.5. There. The total amount of interest earned is $292.50.
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The rate must be in DECIMAL form and the time must be in YEARS
The formula of an area of a circle:

We have
r = 1.8 m
π ≈ 3.14
Substitute:
