Multiply & Add Problems
Solve problems involving multiplying and adding, including using the distributive law, integer scaling problems, and harder correspondence problems
What a learner can do afterwards
- Use the distributive law to solve 14 × 6 as 10 × 6 + 4 × 6
- Solve a scaling problem (e.g. 'A tower is 3 times as tall as a 15 m building')
- Solve a correspondence problem (e.g. '3 types of bread, 4 types of filling — how many different sandwiches?')
The lesson
You already know how to multiply and how to split numbers apart. This time, you'll use both skills together. To multiply a bigger number, split it into two smaller parts, multiply each part, then add the answers.
14 × 6 splits into 10 × 6 and 4 × 6. That gives you 60 + 24, which equals 84.
A shop sells 3 kinds of bread and 4 kinds of filling. Every bread can pair with every filling, so there are 3 × 4 = 12 different sandwiches.
When you split a number apart, every part needs to be multiplied. If you skip a part, your answer comes out too small.
Split a number into parts, multiply each part, then add the results together.
Watch it
Where it sits
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.