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welcome to our video on rounding we're
going to cover two types of rounding
to decimal places and to significant
figures
let's start with a little rule first
the basics of rounding dictate that a
value below a 5 goes to the lower limit
whilst a value of 5 or above goes to the
upper limit
to round 43 to the nearest 10 we isolate
the value we are rounding to
in this case the 4 in the tens column
we add a rounding line to the right of
this
we then look if the value immediately
right is less than 5 or 5 and above
for 43 it's less than 5 so we round down
to 40
replacing the value right of the
rounding line with a zero
for 46 6 is higher than 5
so we round up to 50 again replacing the
digit to the right with a zero
try 45 and 44.8
let's put this into practice with
decimals
if we want to round 5.32 to one decimal
place
this means we need one digit after the
decimal point
imagine if we placed 5.32 on a number
line
we would either round it to its lower
value 5.3 or upper value 5.4
applying the method we have learnt the
digit 2 is immediately to the right of
the rounding line
2 is less than 5
therefore it will go to the lower value
5.3 with the zero not required on the
end
for two or three decimal places apply
the same method just with the rounding
line after the number of decimal places
you need
try pausing and having a go at these
questions
how did you do
significant figures the method of
rounding to significant figures can be
applied to any number of any size
for example the sun is on average 140
million 597
870 kilometers from earth but we tend to
say that it's 150 million kilometers
away
this is the true value rounded to two
significant figures a significant figure
is any number value between one and nine
and inclusive zeros
for example the zero in 3890
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and the zeros in 0.0715
are not significant as they're on the
outside but the first zero in 40
710 is significant as it is within
values between one and nine which is
significant here
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to round to one significant figure
find the first significant value then
add a rounding line to the right side
just as with the decimals applying the
same rounding rules replacing rounded
values with zeros
for example
thirty one thousand two hundred and
forty eight to one significant figure
three is the first so we round the next
value one is less than five so we round
to thirty thousand
to two significant figures try forty two
thousand and eighty five
and zero point six
five
how did you do
so there you have a quick guide of how
to round to decimal places and
significant figures
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until next time