# Problems Involving Proportion

When modelling problems involving proportion it is useful to divide the bar into equal parts so that the proportional relationship and multiplicative structure are exposed.

Once the value of one part is labelled, the other parts can be identified as they are the same, for example in this KS2 SATS Question.

In a class, 18 of the children are girls.

A quarter of the children in the class are boys.

**Altogether, how many children are there in the class?**

The Class |

The bar represents the whole class

Boys |

Folding the bar into quarters allows us to represent the boys as a proportion of the whole class

Boys |

Girls |

Girls |

Girls |

The rest of the class must be girls

Boys |

Girls |

Girls |

Girls |

There are 18 girls so each of the three girl sections must equal 6 and so the boy section must also be 6. 6 × 4 = 24, there are 24 children in the class.