## Purpose of this episode

Practice forward counting in the range 1-10; solve an unknown-addend problem; determine how many items should be added to a set to obtain a desired quantity.

## Description

Children help a scientist build a spaceship. For example, the spaceship has five light bulbs, but it needs nine. Children determine how many more light bulbs are needed and add the bulbs until the spaceship has the correct quantity.

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## Mathematical Background

There are multiple ways to model our experiences in the world using addition. Sometimes we encounter situations dealing with two existing quantities, such as finding how much money I have by adding the amount in my wallet to what I have in my pocket. But some problems are about potential situations, for example, finding how many apples I should
buy if I only have one but I need five to bake a pie. The latter kind of situations require us to perform manipulations with unknowns.

Problems such as finding an unknown addend arise naturally in children’s lives at very early ages, where they are typically approached by forward counting–the technique of counting starting from some initial number, not necessarily from one. Through such problems students develop their understanding of addition and their problem solving skills. Moreover, problems of addition with unknown addend provide a basis for learning more advanced topics like subtraction and even algebra.

## What makes it great?

The progression of the questions helps build understanding.

Children begin the episode by placing concrete objects, reinforcing their understanding of the counting-on strategy for finding an unknown addend. As the episode progresses, the manipulatives are gradually removed, providing a seamless transition from the concrete to the abstract. This experience also seeds ahead to the topic of subtraction.

The scientist’s workshop is a natural setting to explore the mathematical topic- no contrived situations necessary. The children are given the important role of helping the scientist, arousing their curiosity and encouraging perseverance.

The wrong answer feedback gives children the opportunity to learn from their mistakes.

Personalized feedback and hints help children understand where they have gone wrong. At the same time, by keeping the responsibility for completing the task with the child, it encourages accountability. Upon the 3rd wrong answer, the episode provides effective and informative feedback, demonstrating with rich visualizations not only what the right answer is but also how to figure it out.

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