Games
Problems
Go Pro!

Converting to other Bases

Reference > Mathematics > Number Theory > Bases
 

In previous sections, we learned how to convert numbers in other bases into base ten. But what if we have a number in base ten, and we want to convert it into another base?  That's actually a little more complicated, since we're used to working in base ten rather than other bases, so our minds automatically work in base ten.

Probably the best way to explore that question is with an example. Let's suppose you want to convert the number 245 into base twelve. What do you do?

Well, the first thing you should do is to make a list of the place values in base twelve. Remember that the place values are the powers of the base, like 122, 123, and so on. We'll list our place values starting with the ones place, and keep going until we hit a value bigger than the number we're trying to convert.

120 = 1
121 = 12
122 = 144
123 = 1,728

Whoops! That last one is bigger than the number we're trying to convert (245), so we don't need that one.

Since 144 is less than our number, we ask "How many times does 144 go into 245?" The answer is: "1, with a remainder of 101". That tells us that our first digit is going to be a ONE.

Now take the remainder, and the previous place value, and ask, "How many times does 12 go into 101?" The answer is: "8, with a remainder of 5." Now we know that our next digit will be a EIGHT.

Now we take the remainder and the previous place value, and ask, "How many times does 1 go into 5?" Well, that's a silly question - FIVE, of course, with no remainder. So the last digit will be a FIVE.

Therefore, the answer is 185twelve.

EXAMPLE
Convert 59 into base twenty.

First we make our list of powers of 20:

200 = 1
201 = 20
202 = 400, which is too big.

How many times does 20 go into 59? Twice, with a remainder of 19.

How many times does 1 go into 19? 19, with no remainder.

Uh oh...we need the base twenty symbol for the number 19 now! Counting starting with A = 10 and B = 11, we find that J = 19.

Therefore, the answer is 2Jtwenty.

EXAMPLE
Convert 1331 into base eleven.

First we make our list of powers of 11:

110 = 1
111 = 11
112 = 121
113 = 1331
114 = 14641, which is too big.

How many times does 1331 go into 1331? Once, with zero remainder.

How many times does 121 go into 0? Zero times, with zero remainder.

How many times does 11 go into 0? Zero times, with zero remainder.

How many times does 1 go into 0? Zero times.

So the answer is 1000eleven.

Once we obtained a zero remainder, we always had zeroes from that point onward, but we still needed to keep track of our place values, so we would know how many zeroes to put in our result!

Questions

1.
Write 32 in base nine.
2.
Write 120 in base three.
3.
Write the number 1,000,000 in base one hundred.
4.
Write the number 7 in base nine.
5.
How would you convert 12six into base eight? What is the result?
6.
What numbers are written exactly the same no matter what base you're working in?
7.
Find the largest base twenty number which can be written with two digts, if neither of them are letters. What is the value of that number in base ten?
8.
How do you write the number 12 in base twelve?
9.
How do you write the number 18 in base eighteen?
10.
How do you write the number n in base n?
Assign this reference page
Click here to assign this reference page to your students.
Bases Larger than TenBases Larger than Ten
Operations in other BasesOperations in other Bases
 

Featured Games on This Site

Match color, font, and letter in this strategy game
Mastermind variation, with words

Blogs on This Site

Reviews and book lists - books we love!
The site administrator fields questions from visitors.
Like us on Facebook to get updates about new resources
Home
Pro Membership
About
Privacy