Given:
Principal - 1, 728
Maturity Value - 1805.76
Time - 6 months
Find: the amount of interest and the annual interest rate
Solution:
To get the amount of interest, simply subtract the principal amount from the maturity value.
![1805.76-1,728=77.76](https://img.qammunity.org/2023/formulas/mathematics/college/jb85icdepndofbxe6uax3x36u6bucfmla3.png)
Therefore, the amount of interest added is 77.76.
To determine the annual interest rate, we can use the simple interest formula.
![r=(Interest)/(Principal* Time)](https://img.qammunity.org/2023/formulas/mathematics/college/dp517n1xkbhm3psjarouw9wqduxr1c18oz.png)
where:
r = annual rate in decimal
interest = interest added → 77.76
Principal = initial amount → 1, 728
Time = time in years → 6 months or 6/12 or 0.5 year
Let's plug those respective numerical values into the formula above.
![r=(77.76)/(1,728*0.5)](https://img.qammunity.org/2023/formulas/mathematics/college/nz29ssnyyx799sfomw3i692ab6nxbj5hls.png)
![r=(77.76)/(864)](https://img.qammunity.org/2023/formulas/mathematics/college/s9ds3u6wl64ua9l7727u3q6j75wh9gn9gj.png)
![r=0.09](https://img.qammunity.org/2023/formulas/mathematics/college/cr0cj71npu3v0tjh8m329z9pk5ao0eow4r.png)
Therefore, the annual interest rate is 0.09 or 9%.
Situation:
If the air purifier is to be paid in installments for 6 months, there is a 9% annual interest rate that is added to the original price amounting to 77.76.
Assuming average financial income, it would be a good idea to loan based on the calculated interest rate.