Examples: Multiplication, Word Problems Video Lecture - Class 7

hello friends this video on fractions
and decimals part 12 is brought to you
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question number 6 a car runs 16
kilometres using 1 litre of petrol how
much distance will it covered using two
three by four litres of petrol now first
of all 1 litre of petrol covers 16
kilometres so to 3 by 4 litres of petrol
will cover 2 3 by 4 into 16 kilometres
right it is something like this that the
cost of one toffee is 5 rupees then what
would be the cost of 6 stockings the
cost would be 6 multiplied by 5 right so
this would be the distance travelled now
here let's convert this mixed fraction
into improper fraction 4 into 2 plus 3
that is 4 to say 8 plus 3 that is 11 by
4 into 16 now let's multiply the
numerators which would be 176 divided by
denominator that is 4 so it is 176 by
for the can be reduce it to both simpler
form let us look at the factors of 176
and let us also look at the factors of 4
so 176 we would see that it has 1 2 4
and so on as factors and when you look
at 4 it has 1 2 4 the 4 doesn't have any
further factor so the highest common
factor would be 4 so 176 has yet many
more factors but since 4 has only 3
factors so the highest common factor
could be 4 so we can divide the
numerator and denominator by 4 so 176 by
4 is what in fact basically that is what
we could have done here also so this
would be 44 so 44 into 4 is 176 so 44
is the distance that would be traveled
using two three by four litres of petrol
question number seven shade two-third of
the triangles in a box now inside this
box how many total triangles do you have
so total triangles that we see inside
this box is equal to nine
now we have to shade two third of total
triangles that is two third of nine
which is equal to 2/3 into nine so this
would be 18 divided by 3 so again if you
divide it you see 3 into 6 is 18 senses
6 so therefore we can shade 6 strangles
in the box
question number 8 with the end product
went for a picnic their mother gave them
a water bag that contained 5 liters of
water okay with they are consumed 2/5 of
the water
prathab consumed the remaining water how
much water did with their drink so with
they are DANC
2/5 of the water that means 2/5 of how
much water to fifth of 5 liters so this
means 2 by 5 into 5 so this is equal to
10 by 5 and again if you actually divide
it you get it as 2 so therefore they are
drank 2 liters of water what fraction of
the total quantity of water did prathab
drink okay now with the had consumed 2/5
of the water and the remaining part was
consumed by prata now one simple way to
do this is the amount of water that is
drank by prathab will be equal to the
total amount of water that is 5 liters
minus the amount of water which is drunk
by lithium which is equal to 3 liters so
we can say that 3 liters of water is
being consumed by pratap so that is one
way of doing it the other way of doing
it is if we they are consumed 2/5 of
water
means grata consumed how much water
Pratap consumed 1 minus 2 by 5 so 1 is
the complete water because now we are
talking in terms of fraction so 1 is the
total water minus 2/5 which is drunk by
Big Dance so in this case this would be
fine so 1 into 5 is side so this is 1
into 5 minus 2 into 1 so this is equal
to 3 by 5 so Pratap consume 3/5 of the
total water and if you follow by this
procedure in that case you get the
brother drank 3 liters of water so
anyone to find out the fraction you
would say that rata drank 3 liters out
of 5 liters of water so in this case
also you get the same result that Pratap
dragged 3/5 of the remaining water
question number 9 provide the number in
the box such that 3 by 5 multiplied by
dash is equal to 24 by 75 now what have
we learned we learnt that whenever we
multiply two fractions we multiply the
numerators then we multiply the
denominator so basically what happens is
numerator multiplied by numerator gives
the numerator of the product similarly
denominator multiplied by denominator
gives the denominator of the product so
that is the simple rule that we follow
so in this case we have 3 by 5
multiplied by something which we don't
know so let us assume that the something
is say X by Y which is equal to 24 by 75
so this actually means that 3 into X is
equal to 24 so how do you find the eggs
so that means 3 multiplied by something
gives 4 that means that something is
equal to 24 divided by 3 which is equal
to 8
X is 8 what about y5 x y gives 75 so y
is equal to 75 by 5 and this is equal to
15
therefore the number in the box would be
8 by 15 so this would be the number in
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