# birthday cake GCF and LCM

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## Find GCf Using Birthday

Lets find the GCF for 18 21 with Birthday Cake method
Lets find the GCF for 18 21 with Birthday Cake method

Find GCf Using Birthday

## place numbers like so and because 3 goes into 21 and 18 AND is a prime number you put it there

{http://s3.amazonaws.com/engrade-myfiles/4069825408487914/math_diagram_real_one_1.png}

place numbers like so and because 3 goes into 21 and 18 AND is a prime number you put it there

## How many times does 3 go into 21 and 18

{http://s3.amazonaws.com/engrade-myfiles/4033340568962531/math_lesson_diagram_1.png}

How many times does 3 go into 21 and 18

## now add another layer to the "cake" and put the only other prime number that goes into 7 and 9...1

{http://s3.amazonaws.com/engrade-myfiles/4007989452791883/math_lesson_diagram_3_real_one.png}

now add another layer to the "cake" and put the only other prime number that goes into 7 and 9...1

## 1 goes into it 1 time circle 3 and 1

{http://s3.amazonaws.com/engrade-myfiles/4089028863255776/math_lesson_diagram_4_real_one.png}

1 goes into it 1 time circle 3 and 1

## now multiply and theres your GCF

{http://s3.amazonaws.com/engrade-myfiles/4018380651794791/math_diagram_5.png}

now multiply and theres your GCF