Lattice Multiplication
3 Minutes
Lattice multiplication for kids: learn how to multiply two-digit numbers step by step using a grid. A short maths lesson in English.
- Drawing a square grid with diagonals for two-digit numbers
- Multiplying 25 by 13 and writing digits by place value
- Adding diagonally along each family to find the final answer 325
What this lesson teaches
Lattice multiplication is a method used to multiply multi-digit numbers easily by organizing products inside a grid divided by diagonal lines. It breaks a problem down into single-digit multiplications and uses diagonal paths to add the digits by their place value.
Setting up the grid
To multiply two-digit numbers, first draw a large square. Divide the square into four smaller squares by drawing one horizontal line and one vertical line across the middle. Next, write the first number across the top and the second number along the side. Finally, draw a diagonal line through each small square to split every box into two triangles, which separate the tens place from the ones place.
Multiplying each pair of digits
Each digit on top is multiplied by each digit along the side, and the result is written inside the corresponding square. If a product is a single digit, a zero is written in the upper triangle for the tens place and the number itself is placed in the lower triangle for the ones place. For example, when multiplying twenty-five by thirteen, multiplying five by one gives zero and five, while five times three gives one in the tens triangle and five in the ones triangle. Similarly, two times one produces zero and two, and two times three produces zero and six.
Adding along diagonal families
Once all the small squares are filled, the numbers are added diagonally in groups called families. The addition always begins from the bottom right side. In the first diagonal track, there is only the single digit five, which is written down directly. In the next family, the digits six, one, and five are added together to make twelve, so the two is written down and the one is gifted to the next family.
Finding the final answer
The next family contains the digits zero, two, and zero, along with the one that was gifted from the previous addition. Adding these four digits together gives a total of three. The final remaining digit in the top left triangle is zero, which does not need to be written down at the beginning of the number. Reading the collected digits in order gives the final answer of three hundred twenty-five.