Concept of Ratio

We have all learned about ratio in Primary 5 and 6, so we will just give you a quick recap on what is ratio.

In general, a ratio of 2:3 means that the amount of the first ratio is two thirds of the amount of the total quantity. For example, if the first ratio refers to the amount of tables and the second ratio is the number of chairs. It would mean that there are more chairs than tables in the classroom.

Ratios can be easily converted into fractions and percentage. Using the same example, the number of tables is 2/5 of the total number of furniture. The chairs would be 60% of the total amount of stuff.

Question for this Topic:
I have 516 pieces of coloured paper in a plastic bag. They are in 3 different colours, red, yellow and blue, but are not equal in number. The number of red paper is twice the number of blue paper. The yellow paper is 3 times the number of blue paper.
What is the number of

(a) Red paper?
(b) Yellow paper?
(c) Blue paper?

Answer this question in the comments section.

Concept of Speed

Speed is the rate of motion or how fast something moves. It's symbol can be kmph, km/h, or mph

It is calculated simply with the formula Distance x Time. For example, if a van travelled 35km in half an hour, it's travelling speed is 70 km/h.

Speed can likewise be used to find a certain distance or time. For example, if a fighter jet used on national day flew for 12 minutes at 2000km/h across Singapore, the distance it flew is 12/60*2000km which is 1/5*2000km which is 400km!

This is just about what speed is about.

Introduction

Hi everyone,

Welcome to our Math blog!!! Feel free to participate as much as you want and learn all you want to know. You can also drop your comments in the chat box. Most importantly, have fun!

(Sorry for not posting this post earlier.)

Signing off,

Alloy

Kieran

Jiankai

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.