Recipes and the unitary method

Hello, and welcome to Myriora Maths! This pancake recipe makes enough for four people. But six people are coming! How much of everything do we need? Let's find out.

Here's the recipe. For four people, it needs two hundred grams of flour, two eggs, and four hundred millilitres of milk.

First, find the amount for one person. Divide everything by four. Two hundred grams divided by four is fifty grams of flour. Four hundred millilitres divided by four is a hundred millilitres of milk.

Now times by six. Six times fifty grams is three hundred grams of flour. Six times a hundred millilitres is six hundred millilitres of milk. And two eggs for four people is half an egg each, so six people need three eggs.

This is called the unitary method: first find one, then find as many as you need. It works for prices too. If four pens cost two pounds, one pen costs fifty pence, and seven pens cost three pounds fifty.

Let's try one together. Three apples cost ninety pence. How much do five apples cost? Say it out loud!

One apple costs ninety divided by three: thirty pence. Five apples cost five times thirty pence: one pound fifty!

Here's a question that catches lots of people. A recipe for four people needs two hundred grams of flour. How much do six people need? Some people add two, because six is four add two, and say two hundred and two grams. But everything has to grow together, not just by two! Find one person first: fifty grams. Then six people need three hundred grams.

Your turn! Five bottles of juice cost four pounds. How much do eight bottles cost? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! One bottle costs four pounds divided by five: eighty pence. Eight bottles cost eight times eighty pence: six pounds forty!

Quick review. The unitary method: first find the amount for one. Then multiply to find as many as you need. It works for recipes, prices and lots more. Don't just add on: everything has to grow together. See you next time!