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Course: Praxis Core Math > Unit 1
Lesson 2: Number and quantity- Rational number operations | Lesson
- Rational number operations | Worked example
- Ratios and proportions | Lesson
- Ratios and proportions | Worked example
- Percentages | Lesson
- Percentages | Worked example
- Rates | Lesson
- Rates | Worked example
- Naming and ordering numbers | Lesson
- Naming and ordering numbers | Worked example
- Number concepts | Lesson
- Number concepts | Worked example
- Counterexamples | Lesson
- Counterexamples | Worked example
- Pre-algebra word problems | Lesson
- Pre-algebra word problems | Worked example
- Unit reasoning | Lesson
- Unit reasoning | Worked example
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Naming and ordering numbers | Worked example
Sal Khan works through a question on ordering numbers from the Praxis Core Math test.
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Video transcript
- We are asked in the list
above the greatest value is how many times as
large as the least value so pause this video and see
if you can figure that out alright now lets do it together now in order to do this its useful to have all of the numbers in the same format so that we can atleast
compare them an figure out which one is the greatest
and which one is the least so let's convert them all to decimals So this first number right over here that's already in decimal form, 0.004, the next one is also
a decimal already 0.28 or 28 hundredths this next one, one fifth to
convert that into decimal you could go to your calculator or calculator is allowed on the praxis. You could do one divided by five or you might recognize
that one divided by five or one fifth is the
same thing as two tents. Or You could say that 0.2 either way the next one is already a
decimal 0.016 or 16 thousandths and then one over 125 that
might be pretty useful to get a calculator out for that so, and just to show you what I did before the one fifth you could have
just done one divided by five you would've gotten the point two but one divided by 125 is equal to 0.008 or eight thousandths 0.008 now the next thing
we'd want to do is order them and it can be a little
bit misleading because some of these have two digits
to the right of the decimal or actually even one
some of them have three so let's make all of them
have the same number of digits to the right of the decimal point so this one already has three to the right this one could be rewritten a 0.280 this one could be written as 0.200 this one could be rewritten as 0.016 and then this one is already 0.008 so now all of them are
in terms of thousandths so the smallest one
here is four thousandths So let me write that first so that's the smallest one for thousandths and then the next largest
amount of thousandths is this one right over here,
which is eight thousandths then the next largest
one is 16 thousandths then the next largest
one is 200 thousandths and then the largest
one is 280 thousandths so we want to figure out
how many times is large or how many times larger
is 280 thousandths then four thousandths and you might be able
to do that in your head and say oh well 280 divided
by four is going to be 70 or you can go back to a calculator and you could figure it out and you could type in those
exact numbers if you like you could either do 280 divided by four or you could just type in these
numbers exactly as they are 0.280 divided by 0.004 is going to be 70 so this is 70 times larger
than the smallest value and we're done