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Sum

Ten students are to be selected for a project from a class of 30 students. There are 4 students who want to be together either in the project or not in the project. Find the number of possible selections.

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#### Solution

Case I |
Case II |

4 Students are in | 4 Students are out |

Number of ways = ^{26}C_{6} |
Number of ways = ^{26}C_{10} |

Required number = ^{26}C_{6} + ^{26}C_{10}

Concept: Combination

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