Page 23 - E booklet prep 3 bader 2025 b_Neat

2- The proportion

The proportion is the equality of two ratios or more
? ?? = ?? , where a × d = b × c

?? ??

? If a, b , c , are in a proportion ,then ?? = ??

d ?? ??

Mean
Extremses

First case:

?????????? = ??????????

???????????? ????????????

To find one of them we must have the three others and we will make a cross
multiplication

Example 1:

Find the fourth proportional for the numbers 4 , 12 , 16

?? = ????
???? ??

X = ???? ?? ???? = 48
??

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