Saturday, January 23, 2010

22 Jan (01): Prime Factorisation (continues...)

Textbook p9 #25: The three factors are 891, 539 and 2673.
The Prime factorisation of a number is 2^4 X 3^5 X 7^2 X 11.
Write down 3 factors of the number that are greater than 100.
(Hint: 16 X 11 = 176, which is a factor.)

16=2x2x2x2
15=3x3x3x3x3
49=7x7

3x3x3x3x11=891
7x7x11=539
3x3x3x3x3x11=2673


Textbook p9 #26:
The Prime factorisation of two numbers are 2 X 3^2 X 7^3 X 13 and 3 X 7^2 X 13^3 X 17 .
Write down 3 common factors of the numbers.

The three common factors are 2, 3 and 13.

1 comment:

  1. Cheng Ngee

    Textbook p9 #25:
    Note there's mistake in one of the lines
    3^5 = 3x3x3x3x3 = 245

    Indeed, the 3 answers you submitted are correct :D

    Textbook p9 #26:
    Could you elaborate how you arrive at the 3 numbers (2, 3 and 13)?
    Indeed, amongst the 3 numbers you submitted, only "3" and "13" are correct whereas "2" is not the answer.
    Do you have any idea why?
    Could you suggest another common factor?

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