Simple Interest and its Formula

When I first saw this topic, I had no idea what it is about. Actually, simple interest is related to the interest rate when you borrow money. Not your interest in mathematics. Haha!

1. When money is borrowed, interest is charged for the use of that money for a certain period of time.


2. When the money is paid back, the principal (amount of money that was borrowed)(not your school principal) and the interest is paid back. (Imagine if you borrow money and your school principal returns the money for you. HaHa again!)


3. The amount to interest depends on the interest rate, the amount of money borrowed (principal) and the length of time that the money is borrowed.

This is the formula for simple interest is as follows. Interest = Principal * Rate * Time.

(*stands for times(x))

For example, if $100 borrowed from Jane for 2 years at a 10% interest rate, the interest would be $100*10/100*2 = $20. The total amount that she would get would be $100+$20=$120.

Compound interest is similar. Read about it in the next blog post!

Concept of Direct and Inverse Proportion

In mathematics, two quantities are said to be proportional if they vary in such a way that one of the quantities is a constant multiple of the other, or equivalently if they have a constant ratio.
(Wikipedia)

Alright, so what is direct proportion? Direct proportion is when something (must be a number value) is directly related to the proportion something else.

For example, if a car is travelling at at a constant speed of 65km/h, the distance it covers in an hour would be 65km. Therefore, it can be seen that the speed of the car is directly proportionate to the distance the car covers.

Inverse proportion is the exact opposite of direct proportion. So, inverse proportion is when something is inversely related to the proportion of a number value.

For example, let us say that you are driving a car and you are going to travel 70km. Consider this to be a constant distance throughout the following discussion.

1. Suppose that you spent 1 hour driving. Your average speed would be 70 km/h.
   
2. Suppose that you spent 2 hours driving. Your average speed would be 35 km/h.
   So, changing the number of hours that you drive will change the average speed that you will travel.

This is inverse proportion.