Prime Factors, HCFs and LCMs
Express the following as products of prime factors
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400
35000
120000
60
126
405
8100
You might want to now check your answers to the questions above on a calculator before preceding
to the next stage!
Find the high common factors of the following, expressing your answers as a product of prime
factors.
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400 and 60
120000 and 8100
126 and 400
405 and 8100
405 and 126
Find the lowest common multiples of the following, expressing your answers as a product of prome
factors.
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35000 and 8100
126 and 60
400 and 405
35000 and 60
120000 and 126
And finally (still expressing answers as products of prime factors)…..
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What is the HCF of 400, 8100 and 35000
What is the LCM of 126, 400 and 405
If you have not done so already, please create a gmail account so that you can log on to Khan
Academy. (You should check with your parents first as it involves a bit of a white lie about your age.)
If you have some time to spare, I would like you to try to build some familiarity with Kahn Academy.
Try searching for “factors” or “multiples”. Also, Mr Khan talks about Greatest Common Divisors,
rather than HCFs.
There is also a test yourself style exercise at http://www.khanacademy.org/math/arithmetic/factorsmultiples/e
For anyone with some real time on their hands watch how you might calculate the SUM of all the
FACTORS (known as divisors) of 27000.
http://www.khanacademy.org/test-prep/competition-math/v/sum-of-factors-of-27000
SGF