L5 : Questions 1- Integers , Maths, Class 7 Video Lecture

hello friends this video on integers
part 5 is brought to you by example calm
no more fear from exam so now based on
whatever we have studied so far on
integers addition subtraction finding
out bigger and smaller integers we will
quickly look at some of the questions
question number 1 a plane is flying at
the height of 5000 meter above the sea
level at a particular point it is
exactly above a submarine floating 1,200
meters below the sea level what is the
vertical distance between them so let us
first try to draw the diagram so that we
understand it better so we will first
draw the sea level let's say that this
line denotes the sea level now where is
the plane so the aeroplane is somewhere
here let's say this is where you have
the aeroplane so the aeroplane is at a
height of 5,000 meters so that means
this height is 5,000 meters and at a
certain point it is exactly above a
submarine floating 1200 meter below the
sea level so where is the submarine so
the submarine is somewhere here so let
us say this is the submarine and the
distance of the submarine from the sea
level is 1200 meters now what is the
question the question is to find out the
vertical distance between the aeroplane
and the submarine so basically you would
have to find out this total distance so
what would be this total distance now
let us try to consider it like a number
line so if you consider it as a number
line this point which denotes the sea
level would be our origin that is this
sea level would be at 0 and then you
have the aeroplane on the right hand
side at a distance of 5000 meters and on
the left hand side you have the
submarine
the distance of 1200 that is minus 1200
and you have to find the distance
between the two that means you have to
find this entire distance so how would
you find this entire distance so the
entire distance between them would be
nothing but 5000 that is this distance
Plus this distance that is plus 1200
right so when you look at it you might
see that y plus 1200 why not - 1200 now
even if you want to consider the
negative sign in that case it would be
5000 minus minus 1200 this in turn would
mean the same thing so it would actually
mean the same thing right so 5000 plus
1200 which comes out to be 6200 so this
is the vertical distance between the two
so it becomes more evident by looking at
this picture so when you actually want
to add I mean you want to find this
total distance it would be this distance
Plus this distance quick question number
2 in a quiz positive marks are given
four correct answers and negative marks
are given for incorrect answers if Jack
scores in five successive rounds by 25 -
5 - 10 15 and 10 what would what was
this total at the end now in order to
find the total at the end let's say
there were five rounds then the total
score at the end would be given by that
sum of the scores in all the five rounds
so basically total would be equal to 25
plus -5 plus minus 10 plus 15 plus 10 so
this will give you the total so in order
to simplify this addition what we do let
us first add all the positive numbers so
if you add all the positive numbers 25
plus 15 gives 40 plus 10 gives 50 so all
these positive numbers
add together to give 50 plus -5 plus
minus 10 so let us now add the two
negative integers now how do we add two
negative integers we just add them 15
and then put a negative sign and now we
have to add one positive integer at one
negative integer so how do we add them
we find their difference which is 35 and
then put the sign of the bigger number
so bigger number is 50 so 50 has a plus
sign so this will also have a plus sign
so therefore the total score of Jack at
the end would be plus 35 question number
3 Mohan deposits rupees 2000 in his bank
account and withdraws rupees 1642 from
it the next day
if withdrawal of amount from the account
is represented by a negative integer
then how will you represent the amount
deposited okay now if we draw when you
taking it out from the account so let us
say that if this is the bank account
let's say this is Mohan's bank account
so if taking away from the buffer taking
away money from the bank account which
is withdrawal is denoted by a negative
sign so definitely deposit to the
account will be denoted by a positive
sign so amount deposited so deposited
amount will be denoted as plus 2000 now
we have to find out the balance in
moments account so the balance would be
equal to amount deposited so initially
whatever he had deposited minus the
amount which he has withdrawn so this
would be equal to 2,000 minus 1 6 4 2 so
this would be rupees 358 so this would
be the balance in bonds accounting
question number 4 in a Magic Square
each row column and diagonal have the
same sum check if the following is a
magic square now before we talk about
this magic square I hope you understand
what is the meaning of row while haven't
I given what what are the rows here so
this is row number one this is row
number two this is row number three so
these horizontal lines they form rows
whereas this is column number one this
is column number two and this is column
number three so the vertical columns so
they are the columns and what is a
diagonal so this is a diagonal so this 5
2 minus 2 minus 3 this forms a diagonal
similarly 0 minus 2 minus 4 these are
the diagonals right so that's clear from
this now so now we have to find out if
this is a magic square so in order to
find that let us first try to find out
the sum of all the rows so the sum of
first row this is Row 1 Row 2 Row 3 so
we will find out the sum of Row 1 Row 2
and Row 3 so what is the sum of rho 1
this is 5 plus minus 1 plus minus 4 so 5
plus minus 1 plus minus 4 so this is
equal to 0 let us find out some of Row 2
minus 5 plus minus 2 plus 7 so here
minus 5 plus minus 2 would be minus 7
plus 7 which is equal to 0 Row 3 would
be 0 plus 3 plus minus 3 this is also
equal to 0 so we see that sum of all the
roads is 0 now let us try to find out
the sum of the columns so we will find
out some of column 1 column two and
column 3 so column one would be 5 plus
-5 plus 0 which is equal to 0 column 2
would be minus 1 plus minus 2 plus 3
which is again equal to zero and column
three would be minus four plus seven
plus minus three which is also equal to
zero so now we come to the diagonals so
here the sum of the diagonal diagonal
one so when you look at the sum of the
first diagonal so let us call this d1 so
this is 5 plus minus 2 plus minus 3
which comes out to be 5 plus minus 5
that is equal to 0 so now we are left
with the second diagonal which is minus
4 plus minus 2 plus 0 which comes out to
be minus 6 so what do we see we observe
that the sum of all the rolls is 0 sum
of all the columns 0 sum of one diagonal
is also 0 but the last diagonal is not 0
therefore this is not a magic square
because in order to be a Magic Square
all of these should have been 0 both the
diagonals sum should have been 0 but
that is not the case therefore this is
not a magic square thank you please
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