13. 2 Digit x 2 Digit (Numbers up to 40)
In the fourth grade, students are required to multiply two 2-digit numbers. Students can continue to use the same method they had used to multiply 2-digit number by a 1-digit number by making use of area models (distributive property of multiplication). For example, 39 x 21 can be multiplied as (30 x 2) + (30 x 1) + (9 x 2) + (9 x 1). This method of multiplying should acts as a precursor to the standard algorithm. It is important for the students to understand how a particular method works. Fluency with place value (expanded forms), distributive property of multiplication and multiplying multiples of 10 will be of great help here. The 2-digit numbers in 2 Digit x 2 Digit (Numbers up to 40) Worksheet are restricted to those less than 40.
Common Core Alignment
4.NBT.5Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models.