Learning Mathematics Grade 7 | Percentage and its application Video Lecture - Class 7

welcome to Master middle school math
this video can be used as a model for
teachers to teach their own students it
can also be used by students to learn
math and it can also be used by parents
as a model to help their own children
today we will solve percentage problems
using percentage sentences if you're
already very solid on using proportions
to solve percentages that's okay this is
just a different way to do it here's
some background information I just want
you to think about this always and keep
this in mind percent means of 100 that's
what the word means and a quick easy way
to remember that is to look at the
percentage sign and you've got the 1 0-0
100 C so here is our percentage sentence
this is the format this is what it will
always look like you're going to read it
from left to right like you read a
written sentence we're gonna take our
written sentence and convert it into
mathematical sentence so the first blank
is always the original amount the
principle of means that you're going to
use the operation of multiplication so
you can have a time symbol and then
percentage it gets converted to a
decimal number and we will talk about
that later to do the computation is
means the equal sign and the answer is
the product of the question so let's
look at a written sentence what is so
what means we don't know that's a
question so is is the clue so it's going
to be the answer we're looking for 50%
is going to be converted into a decimal
number so that goes into the decimal
blank of 100 is our clue so we're
multiplying 100 100 is going to be our
principal amount so let's write it down
in a mathematical form 100 times point
50 equals we don't know we're looking
for that remember how we talked about
changed up percentage into a decimal
number in order to do the computation to
do the arithmetic well I'm going to show
you how to do that so our first step is
just to eliminate the percentage
then we're gonna move the decimal point
two places to the left
and you might say I don't see a decimal
point but let me tell you a little
secret every number has a decimal point
sometimes it's in the beginning
sometimes it's in the middle and
sometimes it's at the end if it's at the
end of the number it almost always is
invisible but it's still there it's just
invisible so we're gonna write it in to
remind us that it's there even though
it's invisible we're going to move it
two places to the left one two you
always always move it two places to the
left and you might say how will I
remember in what direction to move it
well what I do is I think about the
alphabet the alphabet is something we
all know it's been in front of the
classroom forever you probably sang
songs about it in kindergarten so when
you look at the alphabet D is to the
left of P and the word decimal starts
with D and the word % starts with P so
when we're going from percent to decimal
we go two places to the left because D
is to the left of P well here's our 50%
let's do it again very quickly you
eliminate the sign you move your decimal
point that's invisible you move it two
places to the left because you're going
from percent to decimal P to D now
here's our percentage sentence and we
have the original this is the structure
of percent is the answer the product we
have a question here what is 40 percent
of 150 so in this case we're looking for
the answer what is is gives us the
little hint there so we're gonna rewrite
our problem mathematically reading it
from left to right 150 is going to go
into the principal slot of we're gonna
change 40% 2.40 is we don't know we're
going to find out that answer so we do
the math 150 times point 40 equals 60
here is another sentence that we're
going to read from left to right and now
we're going to fill in the blanks but
first we have to figure out what we're
looking for in this case 25 is what
percent of
50 what percent so in this case we're
looking for the percent so when we fill
in our blanks 250 of question mark is 25
so we've noticed that you've put in
numbers and symbols in different places
based on the question now when we have
our normal problem with both parts of
the question and we're trying to find
the answer the product we multiply in
this case we have the answer already and
we're looking for part of the question
so we're going to do the opposite of
multiplying which is division and so we
have 25 divided by 250 equals point 10
now point 10 is a decimal number we're
looking for a percentage so we're going
to do the opposite of what we did before
we went from percent to decimal now
we're going to have decimal so we're
gonna look at our alphabet we'll notice
that P is to the right of D so we're
gonna move our decimal point two places
to the right it's at the end of the
number so it can disappear we don't have
to have it written and we're going to
add our % so our answer is 25 is 10
percent of 250 so now here's another
question 40 is 20 percent of what so now
this time we're looking for the
principal amount the original amount
because the of gives us that little hint
so we're gonna fill it in question mark
we don't know the original x point when
T is 40 and so we're gonna write it out
mathematically
remember we're dividing now because we
have part of the question and the answer
so we have to do the opposite so we're
dividing 40 divided by point 20 equals
200 answer is 40 is 20 percent of 200
let's recap this is our percentage
sentence structure we read it from left
to right the first blank is the original
the principal amount of means
multiplication the percent becomes a
decimal number for computation to do the
arithmetic
is means the equal sign and the answer
is the product of the question then we
have to change our percent and our
decimals back and forth and the way we
remember that as we move our decimal
point we look at the alphabet as our
little reminder and if we're going from
decimal to percentage we're going to
move it two places to the right and if
we're going from percent to decimal
we're going to move it two places to the
left here is some of the academic
vocabulary that we use during this
lesson remember you're going to take
these words and write the definition in
your own words and draw pictures so it's
easy for you to remember their meanings
percent decimal numbers multiply divide
product and computation I hope you found
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