L17 : Questions - Rational Numbers , Maths, Class 7 Video Lecture

hello friends this video on rational
numbers part 17 is brought to you by
exam feel calm no more fear from exam so
based on the addition subtraction
multiplication and division let us
happen to get some of the questions
question number one find the sum - 8 by
19 plus minus 2 by 57 so in this case we
have different denominators so what will
we do we will find out the LCM of the
two denominators so that LCM of nineteen
and fifty seven would be 57 so therefore
minus 8 by 19 so what can you multiply
so that you get denominator as
fifty-seven so 19 into three is 57 so
you multiply the numerator and
denominator by three so you get minus 24
by 57 so therefore minus 8 by 19 can be
written as minus 24 by 57 plus minus 2
by 57 so now you have same denominator
therefore you can just add the
numerators so this would mean by this 24
+ -2 divided by 57 this is equal to
minus 26 divided by 57 so this would be
the answer question number 2 5 by 63 -
minus 6 by 21 now the number which is
getting subtracted is nothing but it is
same as adding it's additive inverse so
you add the additive inverse of minus 6
by 21 which is nothing but 6 5 21 so it
is asked so it is as good as adding 5 by
63 and 6 by 21 so here also you have
different denominators so let us find
out LCM of 21 and 63 which is nothing
but 63 so therefore here for the first
term it is already 63 so what about the
second term so 6 by 21 what will you
multiply so that you get 63 as the
denominator
you're multiplying it with three so you
get 18 by 63 therefore this can be
written as five by 63 plus 18 by 63 so
this would be 5 plus 18 divided by 63
that is equal to 23 by 63 so this would
be the answer question number 3 find the
product minus 6 divided by 5 multiplied
by 9 by 11 just multiply the numerators
multiply the denominator separately so
when you multiply the numerators you get
minus 54 when you multiply the
denominators you get 55 so minus 54 by
55 is the product question number 4 find
the value of minus 4 divided by 2 by 3
so the number that is getting divided so
that is dividing basically so minus
we'll divide it by 2 by 3 so this is
same as minus 4 multiplied by the
reciprocal of 2 by 3 so just interchange
then numerator and the denominator so
here this is a simple multiplication so
minus 4 is minus 4 by 1 so multiply the
numerator so this would give you minus
12 multiply the denominators that would
give you 2 so this would be 2 6 is a 12
so the answer would be minus 6 so with
this we have reached towards the end of
this lesson on rational numbers and I
hope that this lesson would have helped
you so here we have dealt with all the
basic properties and basic operations
and rational numbers
try to solve more and more questions
which will help you to build your
confidence and concepts so I hope this
lesson would have helped you see you on
in the next lesson thank you please
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