AWM+11+Ch+0_1+Solving+Proportions

__ Chapter Zero - topic one - **Solving Proportions** __ A **proportion** is an equation between two ratios (or fractions). Examples:  Notice that in all true proportions, the cross-products are equal. In the above examples: 6 x 5 = 15 x 2 = **30** 48 x 25 = 100 x 12 = **1200** This gives us a quick method in solving proportions with one unknown. We shall call this method “solving by **cross-multiplying**”. Watch a clip on YouTube on how to solve a proportion. Ex 1: //In a group of 250 students, 36% of them are male. How many students are male?// Solution: Write the percentage as a fraction --->  (Note that 36 represents the “part” and 100 represents the “whole”) Since 250 students represent the “whole”, it is at the same level as 100. Using //x// as the unknown for the number of male students in the group, we write --->  Cross-multiplying, we get ---> (36)(250) = (100)(x) ---> 9000 = 100x ---> 90 = x [dividing both sides by 100] There are 90 male students in the group.

Ex 2: //At a technical institute, there are 112 students in the electrician program. This represents 14% of the student population. How many students are there in total at this institute?// [answer: 800]