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## #1 2021-12-08 10:57:20

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 330

### proportionality

Hi,
y = 2x + 1
the y is not directly proportional with x because the function is not like that : y=kx
because of number +1
my question is how this number "+1+ effected on these quantity that made them not proportional to each other

my second question is : I saw this image in mathIsFun site talking about proportions (https://www.mathsisfun.com/algebra/proportions.html)

from this image I can see the white dog head is 10 and the other brown dog head is 15
also the body of white dog is 20 and body of brown dog is 30 => 10/20 = 15/30
how cold they become equal?
how can I make these quantities equal and right "=" between them
I read a lot of that and it's useful to solve some problems like finding the percent... etc
but I still can't imagine how they are equal and how could we right "equality" between them
I mean look they are different sizes
I know if I multiply the two quantity by 2 for example they will get larger is equal the head will become 20 and the other head will become 30, it's like ratio between them, but I still can not imagine how can I write equal sign between them because one is bigger from another

Wisdom is a tree which grows in the heart and fruits on the tongue

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## #2 2021-12-08 21:00:56

Bob
Registered: 2010-06-20
Posts: 9,358

### Re: proportionality

I know if I multiply the two quantity by 2 for example they will get larger is equal the head will become 20 and the other head will become 30, it's like ratio between them,

This line tells me that you are understanding this correctly.

The ratio of head : body length is 1:2

One way of expressing ratio is to use fractions.  In words you could say "the head length is half the body length.

In fractions

This is a true statement about fractions that has nothing to do with body sizes in dogs.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

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