# Calculate the Greatest Common Factor or GCF of 1240

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The instructions to find the GCF of 1240 are the next:

## 1. Decompose all numbers into prime factors

1240 | 2 |

620 | 2 |

310 | 2 |

155 | 5 |

31 | 31 |

1 |

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

Prime factors of 1240 | = | 2^{3} . 5 . 31 |

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

Common prime factors: 2 , 5 , 31

Common prime factors with the lowest exponent: 2^{3}, 5^{1}, 31^{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^{3}. 5^{1}. 31^{1} = 1240

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