How to teach your kid fractions in the kitchen: halves, thirds and doubling recipes

Fractions are where a lot of kids first decide they're "not math people." On paper, ⅔ and ¾ are just confusing symbols. But in the kitchen, ¾ cup of flour or half a sandwich is something you can see, hold and eat. That's why the kitchen is one of the best fraction classrooms there is.

Why fractions matter so much

They're a gateway to later math. In a 2012 study that followed 212 children from sixth to seventh grade, sixth graders' understanding of fractions predicted how much their overall math achievement grew the next year, even after accounting for things like working memory, intelligence and whole-number arithmetic skills. The reverse wasn't true: general math achievement didn't predict later fraction gains. That's one study, so it shows a link rather than proof, but it suggests fractions are worth getting right.

Start with sharing. The U.S. Institute of Education Sciences' guide on teaching fractions recommends building on children's informal understanding of sharing and proportionality to develop early fraction ideas. Its next recommendation, with moderate evidence: help children see that fractions are numbers, not just pieces of a pizza.

What schools expect: in schools using the Common Core standards, third graders learn that a fraction like ⅓ is one part when a whole is split into 3 equal parts, mostly with halves, thirds, fourths, sixths and eighths. Fourth graders learn to multiply a fraction by a whole number, which is exactly what doubling a recipe is.

Skill 1: Cut food into halves, thirds and quarters

1. Your grown-up watches while you cut.
2. Cut one piece in half: two equal parts.
3. Cut another into thirds, then one into quarters.
4. Check the pieces are the same size.

Use soft foods like bread, a banana or a quesadilla, and a kid-safe knife. (More in knife skills.)

The big idea is equal. Two pieces aren't halves unless they're the same size. Ask: "If I cut it like this, are these halves?" (Lopsided pieces make the point fast, especially when a sibling gets the small one.)

Thirds are tricky, and that's the point. Halves and quarters are easy: cut, then cut again. Thirds need planning. Let your child figure out how.

Then compare: "Would you rather have ⅓ of the sandwich or ¼?" Many kids say ¼ because 4 is bigger than 3, until they see the pieces side by side.

Skill 2: Double a small recipe

1. Read each amount in the recipe.
2. Multiply each amount by two.
3. Write the new amounts down.
4. Ask your grown-up to check your math.

The ¾ line is the real learning. ¾ + ¾ = 6/4 = 1½. Use measuring spoons to prove it: three ¼ teaspoons, twice, makes six quarter-teaspoons, which is one and a half.

The challenge: halve or double a full recipe, and cook it

The mastery goal is to halve or double a full recipe and cook it correctly.

1. Halve or double every amount on paper.
2. Your grown-up checks it and stays nearby.
3. Measure each new amount carefully.
4. Cook it and taste the result.

Halving is harder than doubling. Half of ¾ cup is ⅜ cup, and there's no ⅜ cup measure. Your child has to figure out a workaround: ¼ cup plus 2 tablespoons. (There are 16 tablespoons in a cup, a handy fact for this.)

The taste test is the proof. If the cookies come out flat or salty, something went wrong in the math. Go back and find it together.

Safety: a grown-up stays in the kitchen for anything with a stove, oven or knife. (More in following a recipe.)

Make it a quest

In Family Quests, this is the Fraction Chef skill. Practice quests are cut food into halves, thirds and quarters and double a small recipe, and the mastery quest is halve or double a full recipe and cook it correctly. Every Fraction Chef quest lists a grown-up as part of the job, and you approve each quest before it counts. Start free.

Next: teach your kid percents and unit prices, or go back to measuring.