The students will need 12 shelves in all.

**Step 1 **

Use the clues to find how many books there are of each kind.

**Kind of Book** |
**Books per Shelf** |
**Information From Clue** |
**Number Sentence to Find the Number of Books** |
**Number of Books** |

Picture |
93 |
The number of picture books is 9 times the number of student dictionaries. |
31 × 9 = 279 |
279 |

Fiction |
63 |
7 times as many fiction books as biographies |
54 × 7 = 378 |
378 |

Dictionaries |
31 |
23 fewer dictionaries than biographies |
54 – 23 = 31 |
31 |

Biographies |
27 |
There are 54 biographies. |
54 is given in the clue. |
54 |

**Step 2 **

Write a division sentence to find out how many shelves are needed for each kind of book.

**Kind of Book** |
**Number of Books** |
**Books per Shelf** |
**Division Sentence to Find the Number of Shelves
(Total Number of Books ÷ Number per Shelf)
** |
**Number of Shelves Needed** |

Picture |
279 |
93 |
279 ÷ 93 = 3 |
3 |

Fiction |
378 |
63 |
378 ÷ 63 = 6 |
6 |

Dictionaries |
31 |
31 |
31 ÷ 31 = 1 |
1 |

Biographies |
54 |
27 |
54 ÷ 27 = 2 |
2 |

**Step 3**

Add the number of shelves needed for each kind of book to find the total number of shelves needed for the library.

**3 + 6 + 1 + 2 = 12 shelves in all**