# Calculate the Greatest Common Factor or GCF of 1220

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The instructions to find the GCF of 1220 are the next:

## 1. Decompose all numbers into prime factors

1220 | 2 |

610 | 2 |

305 | 5 |

61 | 61 |

1 |

## 2. Write all numbers as the product of its prime factors

Prime factors of 1220 | = | 2^{2} . 5 . 61 |

## 3. Choose the common prime factors with the lowest exponent

Common prime factors: 2 , 5 , 61

Common prime factors with the lowest exponent: 2^{2}, 5^{1}, 61^{1}

## 4. Calculate the Greatest Common Factor or GCF

Remember, to find the GCF of several numbers you must multiply the common prime factors with the lowest exponent.

**GCF** = 2^{2}. 5^{1}. 61^{1} = 1220

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