What is Proportion? Video Lecture - Class 7

hello everyone let's start today with a
new lesson on ratio and proportion
first let's have a look at what exactly
is ratio
comparing to quantities by division is
called ratio the ratio form of 3/2 is
written as 3 ratio 2 and is read as 3 is
to 2 in the ratio 3 they should 2 3 & 2
are both called the terms of the ratio
fractional form we write it like 3/2 and
in ratio form we use colon mark and
write 3 ratio do now we have some
important points first point says the
two quantities compared should be of the
same kind
now this is very important because we
cannot compare rupees 105 mangos the
quantities have to be same either you
compare rupee to rupee or mangos to
mandals
second point says two or more quantities
compared should be expressed in the same
unit again let's have a look ratio of
rupees five to 30 passive has to be
precisely written like five hundred
passe to 30% or rupees five two rupees
0.30 you cannot compare rupees and pass
it otherwise
Third Point raise the names or units of
two quantities should not be used in
ratio ratio of five meter to 6 meter
cannot be written like five meter ratio
six meter
please remember everyone the ratios are
expressionless unit less quantities we
are basically comparing two things so
when you compare two things you do not
ever write units next point says ratio
should always be expressed in the
simplest possible form let's have a look
well ratio 24 should be written as 1
ratio 2 because both are divisible by 12
same way 14 ratio 16 should be written
as 7 ratio 8 because both the terms are
divisible by 2 next we move on to
proportion
a statement of the quality of ratios is
called proportion let's have a look
6 upon 10 we can write it like 3 upon 5
in the lowest possible form same way 48
upon ad we can write it like 3 upon 5 in
the lowest possible form both the
numbers are divisible by 8 and then by 2
thus we can say that 6 1048 and 80 are
in proportion why we said that these
turn numbers are in proportion because
they gave us the same ratio of the being
divided
thus we write 6 ratio 10 is proportional
to 48 ratio in D and we read it like
what 6 is to 10 as 48 is to 80
the numbers 6:10 4880 are called terms
of proportion now let's try and
understand this topic six becomes our
first term then becomes the second term
48 third term and 84 term six and eight
D these are at the extreme ends first
and fourth therefore these are known as
extremes the middle term
those are second term and third term and
and forty-eight are known as means now
always remembers product of extremes
here is 6 into 80 that comes out to be
480 product of means is equal to 10 into
48 that is 480 both the products are
equal that is product of extremes is
equal to product of means
if such a case arises that shows that
the phone numbers are in same proportion
thus if four numbers are in proportion
then product of extremes has to be equal
to the product of means this is how we
verify whether four given numbers are in
proportion or not
next we move forward to continued
proportion if three numbers ABC are in
proportion such that a ratio B is
proportion to 4b ratio C then ABC are
said to be in continued proportion for
example let's have a look take numbers 2
10 and 50 these three numbers are in
continued proportion because two ratio
10 is 1 ratio 5 10 ratio 50 is also 1
ratio file so that means 2 ratio 10 is
proportional do then ratio 50
thus if a ratio B is proportional to B
ratio C and we know that product of
means is equal to product of extremes
therefore B square is equal to AC please
remember this is a very important
formula for continual proportion product
of means becomes P Square and product of
extremes is AC and it will always be
equal
hope you like this listen see you soon
with a new lesson on percentage thank
you