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welcome to math with mr j

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in this video i'm going to cover how to

calculate a discount by hand so we are

going to write everything out without

using a calculator this will show all of

the steps for calculating a discount and

then the final sale price based on that

discount let's jump into our example

where we have 35 percent off of 78.30

now the first thing that we need to do

is to calculate the discount so how much

money will be taken off the original

price we do this by multiplying the

original price

by the rate of discount the rate of

discount is in the form of a percent so

we need to convert that percent to

decimal form percent means per 100 so we

divide our percent by 100 to convert it

to a decimal we can do this by simply

moving the decimal twice to the left so

for our example let's move the decimal

twice to the left to change it to

decimal form so i'm going to rewrite 35

percent

underneath here so i have enough room

now 35 percent that's a whole number so

our decimal comes at the end of a whole

number we typically don't write it in

there because we do not need it with it

being a whole number let's move it twice

to the left

once

twice

so it's going to come before the three

so we have

0.35 that's our decimal form of 35

so once we have that we take our

original price

and 78.9

cents and multiply it by that rate of

discount in decimal form so let's write

that out

78 dollars

and 95 cents

times

35 percent in decimal form so 0.35

so let's calculate that and i'm going to

come to the right in order to go through

those steps now when we multiply

decimals we can take the decimals out

and then place the decimal in the answer

once we get to that point so i'm going

to take the decimals out and multiply

seven

eight

nine five

times

thirty five and again we will worry

about the decimal at the end

five times five is twenty-five

five times nine is forty-five plus two

is forty-seven

five times eight is forty plus four is

forty-four

and then five times seven is thirty-five

plus four is

thirty-nine we are done with this five

and then the two four and four we need

our placeholder zero because we are

moving one place value to the left and

now we can do three times five which is

fifteen

three times nine is twenty-seven plus

one is twenty-eight

three times eight is twenty-four plus

two is twenty-six

and then 3 times 7 is 21 plus 2

is 23

so now we

add here

5 plus 0 is 5. 7 plus 5

is 12

1 plus 4 is 5 plus 8 is 13.

1 plus 9 is 10 plus 6 is sixteen

one plus three is four plus three is

seven

and then we have a two

so now we're ready to place our decimal

so we look back at the original problem

and see how many digits are to the right

of a decimal or how many digits are

behind a decimal well we have 1

2

3

4. so that's how many digits are going

to be to the right of the decimal in our

answer so we can count off

one

two

three

four digits our decimal is going to be

placed in between the 7

and the 6 so we get let me rewrite this

without the lines underneath

so we get

two 27.6325 now we are working with

money so we need to round this to the

hundredths place we have a three in the

hundredths place

look at the digit to the right we have a

two that two says we stay the same so we

are going to get

27

and 63 cents so 78 dollars and 95 cents

times 0.35

i ran out of room here so i'm going to

write it above that gives us

27

and

63

cents

so that's our discount that's how much

money we are taking off the original

price that's 35

of 78. and 95 cents so once we have that

information we can subtract that

discount from the original price so the

original price minus the discount we are

taking the discount off of the original

price

the original price

78

95

and we are subtracting

27

63

so let's see what our sale price is

going to be

now when we subtract decimals we need to

line the decimals up so i'm going to

calculate this to the right so we have

78 dollars

and 95 cents

minus

27.50

and 63 cents so the decimals are lined

up and that's going to line up all of

our places let's start by subtracting

the hundredths so 5 minus 3 gives us two

then we have nine minus six

that's three

we bring our decimal straight down it's

lined up throughout the entire problem

eight minus seven

one and then seven minus 2

which is 5. so we get

51

32 so 51

and 32 cents so that is going to be our

sale price so let me rewrite that 51

and 32 cents

this is our final sale price 51

and 32 cents

so there you have it there's how you

calculate a discount by hand i hope that

helped

thanks so much for watching

until next time

peace

you