L6 : Questions 2 : Fraction - Fractions and Decimals , Maths, Class 7 Video Lecture

hello friends this video on fractions
and decimals part six is brought to you
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exam question number three a rectangular
sheet of paper is 12 1 by 2 centimeter
long and 10 2 by 3 centimeters wide so
you have a rectangular sheet of paper
something like this so the length is
given this is the event and this is the
width which is also called the breadth
find its perimeter so perimeter is
nothing but the boundary so we can say
that perimeter will be equal to length
plus bread plus length plus spread so
that means basically the perimeter is
equal to 2 into length plus breadth that
would be the perimeter because perimeter
is actually length plus width plus
length plus bread this is L be again L
again B so this is this would be equal
to 2l plus 2 B which can be written as 2
into length plus bread then the question
the length is given as 12 1 by 2 and the
breadth is given by given as 10 2 by 3
so that means we will have to find out 2
into 12 1 by 3 plus 10 2 by 3 so how can
we add two mixed fractions first of all
we need to convert them into improper
fractions how do we do that 12 into 2
plus 1 that is 24 plus 1 which is 25 by
2 plus 10 into 3 30 plus 2 that is 32 so
32 by 3 so now what do we do how do we
add these two fractions look at the
denominator they have different
denominators so we will find out LCM of
2 and 3 so LCM of 2 & 3
is equal to six so their food the
denominator will have 6 2 into 3 is
equal to 6 therefore 25 into 3 plus 3
into 2 is equal to 6 therefore 32 into 2
so this is equal to 2 into 25 into 3 is
75 32 into 2 is 64 this divided by 6 so
this is equal to 2 into 75 plus 64 is
equal to 139 divided by 6 thank so this
becomes equal to 2 into 139 divided by 6
now we know that 2 into 3 is equal to 6
therefore this is 1 39 divided by 3 so
this match centimeters would be the
answer now if you want you can convert
this into mixed fraction again for that
you'll have to divide 139 by 3 so I hope
you'll be able to do that yourself so
let's look at the next question question
number 4 Sally wants to put a picture in
a frame the picture is 7 3 by 5
centimeters wide to fit in the frame the
picture cannot be more than 7 3 by 10
centimeters wide how much should the
picture be trimmed let us say that this
is the frame so this is the frame so let
us draw it like this now this is our
frame now what about the picture the
picture is slightly bigger than the
frame so the picture may be let us draw
it like this so the picture is maybe
this much so this is the picture now if
we want this picture to fit into the
spring do you think it will fit into the
frame no so we will have to trim this
much fat so this much part needs to be
removed so in this question we have to
find out that how much is this part
which needs to be removed so how will we
find out
despite this total width of the picture
subtracted and from there we will
subtract them they are width of the
frame right so that that's what we will
have to do so we will have to find out
the difference so with how do I find the
difference which is a bigger number 7 3
by 5 or 7 3 by 10 now logically we can
understand that the picture is bigger
that is why we are trimming the picture
the picture is being cut that means that
the picture is bigger so the width of
the picture is 7 3 by 5 so from 7 3 by 5
we subtract 7 3 by 10 so as we know
first of all we will convert the mixed
fractions into improper fractions so 7
into 535 plus three that is 38 divided
by 5 minus 7 into 10 70 plus 3 that is
73 divided by 10 in this case again you
have different denominators so you find
out the LCM of 5 and 10 which is 10 the
5 into 2 is equal to 10 therefore 38
into 2 minus 10 into 1 is equal to 10 so
73 into 1 now this is equal to 76 minus
73 divided by 10 which is equal to 3 by
10 so 3 by 10 centimeters needs to be
trimmed from the picture question number
5 Michael finished coloring a picture in
7 by 12 hours we have finished coloring
the same picture in 3 by 4 hour who
worked longer by what fraction was it
longer so basically we will have to find
out whether 7 by 12 is bigger or 3 by 4
is bigger so we are given two fractions
7 by 12 and 3 by 4 so both of them have
different denominators so let us first
try to convert them into like fractions
so for that we
find out LCM of four and twelve that is
the denominators so what would be the
LCM of four and twelve four ones are
four four threes twelve so three one one
so the LCM would be 4 into 3 which is
equal to 12 so the LCM is 12
now therefore 7 by 12 can be written as
DS what about 3 by 4 in case of 3 by 4
we multiply the numerator and
denominator with such numbers that the
denominator in the result is 12 so 4
into 3 is 12 so we also multiply the
numerator by 3 so this becomes 9 by 12
so now we have two numbers 7 by 12 and 9
by 12 so we can say that 9 is greater
than 7
therefore 9 by 12 is greater than 7 by
12 or 3 by 4 is greater than 7 by 12 so
what is 3 who worked for 3 by 4 hours
we're home so therefore we can see that
VIPRE worked longer now the next part of
the question see is by what fraction
wasn't longer that means how much was
the difference between the groups
working hours and Michaels working hours
so for that we will have to find out the
difference between the two so how do you
find the difference the your number that
is 3 by 4 minus 7 by 12 say in the LCM
of 4 and 12 is 12 so the denominator
would be 12 4 into 3 is 12 so this would
be 3 into 3 minus 12 into 1 is 12 so
this would be 72 1 so 9 minus 7 by 12
which is equal to 2 by 12 so 2 into 6 is
12 so this is equal to 1 by 6 hours so
the difference between the two is 1 by 6
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