Ratio and Proportion

Like fractions, ratio and proportion has already been studied in our earlier days. And it is just as important to the real world.  

A ratio is a relationship between two numbers of the same kind like a:b
A proportion is an equation a:b = c:d stating that two ratios are equivalent.

Sample problems:

15ft to 45 ft
Solution:in this problem, get the lowest term of the two numbers which is 15
                =15 is 1 and 45 is 3 so
                =15/45 = 1/3

30 minutes to 2 hours
Solution: convert first the hours into minutes which is 1 hour = 60 minutes
               = 2*60 = 120
               = 30 minutes and 120 minutes, get the lowest term which 30
               = 30 is 1 and 120 is 4
               = 30/60 = 1/4

If 2 ballpen cost 20 php. How many ballpens will she have if he has 320php
Solution: make a proportion formula and represent the second ballpen with x
                 = 2 ballpen                x ballpen
                   -------------     =     --------------
                    20 pesos                 320 pesos
                 = cross multiply
                      2*320 = 640 and 20* x = 20x
                 = 640 = 20x divide the number by 20 (to make the x an individual number)
               
                 = 640    20x   = 32 = x
                    -----   ------
                     20      20
                 = she will have 32 pencils

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Prof. Cris Paner