Ratio and Proportion

Let us learn about ratio and proportion,
Ratio is a concept that you have probably encountered in other math classes. It is a comparison of sizes.

Ratio :

The ratio of two numbers a and b is the fraction , usually expressed in reduced form. An alternative form involves a colon. The colon form is most frequently used when comparing three or more numbers to each other. See Table 1 .

TABLE 1 Ratio Formats Ratio Written Form 3 to 4 3/4 or 3 : 4 a to b, b ≠ 0 a/b or a : b 1 to 3 to 5 1 : 3 : 5

Example 1: A classroom has 25 boys and 15 girls. What is the ratio of boys to girls?




The ratio of boys to girls is 5 to 3, or 5/3, or 5 : 3.
Example 2: The ratio of two supplementary angles is 2 to 3. Find the measure of each angle.

• The angles have measures of 72° and 108°.
  
• 2 x to 3 x reduces to 2 to 3.
  
• 2 x + 3 x = 180° (The sum of supplementary angles is 180°.)
  
• 5 x = 180°
  
• x = 36°
  
• Then, 2 x = 2(36°) and 3 x = 3(36°).
  
• So, 2 x = 72° and 3 x = 108°

The angles have measures of 72° and 108°.

Hope the above explanation helped.