# How Do I Do A “ Facturo

### Presentations text content in How Do I Do A “ Facturo

How Do I Do A “Facturo?”

A Facturo is like a crossword puzzle, except each “clue” is a factorable number, and the “letters” are its prime factors. No guessing!Factor all of the clues into primes – put them in order in the clues sectionIn the puzzle, pick an intersection of an across clue and a down clueWhen only one prime is common to both clues:write the prime in the intersection and cross it off in both matching clue factorsFill in any other primes that must fit – work your way from there

3 3 5

2 5

45

/ \ 9 5 / \ 3 3

5

/

/

2

3

3

6 = __ x __

Slide2Factor all the “clues” into primesPrimes are 2, 3, 5, 7, 11, 13, 17, 19, 23, etc

(any number that can only be 1 x itself)Three easy tests for 2, 5, and 3:2 is the only even number prime. All other even numbers have at least one factor of 2All numbers ending in 0 or 5 have a factor of 5To see if 3 is a factor, add up a number’s digits;if that sum divides evenly by 3 then so does the numberFor higher primes (like 7, 11, 13, etc) use long division to see it’s a factor

Slide3Tools for breaking a number into PrimesMultiplication Table – Simple products 14 = 2 x 7

12 = 2 x 6 = 2 x 2 x 3Factor Trees – start with smaller primes 20 / \ 2 10 / \ 2 5 so 20 = 2 x 2 x 5Shorthand Division – for dividing by 2, 3, 5 102 (2 goes into 10 5 times with no remainder. 2 goes into 2 one time.) / \ 2 521 (3 goes into 5 once, with 2 remainder. Carry the 2 making 1 into 21. / \ 3 goes into 21 7 times.)

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## How Do I Do A “ Facturo

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