Evaluating formulas

# Evaluating formulas

Before you start there are some simple formulas to evaluate on page 5.

#### Question 1

A rule to calculate the amount of medicine (mL) a child needs is:

Child amount = (Adult amount × Age of child) ÷ (Age of child + 12)

Adult amount (mL) |
Age of child (years) |
Child amount (mL) |
---|---|---|

10 | 8 |

#### Solution

Substitute in the formula. This formula is known as Young's rule and uses age to calculate the dosage.

Child amount | = (10 × 8) ÷ (8 + 12)(Evaluate the brackets first.) |

= 80 ÷ 20 | |

= 4 mL. |

Check that your answer is less than the amount for an adult.

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