Multi-digit multiplication - 4th grade

We go through several calculations that involve parentheses, multiplication, division, addition, and subtraction, using the correct order of operations. Then, the lesson focuses on WRITING simple expressions from word descriptions or for real-life situations. This skill prepares children for algebra -- because putting several operations together into a single "number sentence" or expression involves algebraic thinking.

We go through several calculations that involve parentheses, multiplication, division, addition, and subtraction, using the correct order of operations. Then, the lesson focuses on WRITING simple expressions from word descriptions or for real-life situations. This skill prepares children for algebra -- because putting several operations together into a single "number sentence" or expression involves algebraic thinking.

Just a word problem for about 4th grade that gives info for the wages of two persons (Mathy my mascot and Abby), and asks who earns more in a week, and how much more. We need to use 2-digit multiplication to solve it. The first part of this lesson is here: In it, we learn a shortcut for two-digit multiplications where one number is a multiple of ten (such as 24 x 30 or 98 x 60),

Just a word problem for about 4th grade that gives info for the wages of two persons (Mathy my mascot and Abby), and asks who earns more in a week, and how much more. We need to use 2-digit multiplication to solve it. The first part of this lesson is here: In it, we learn a shortcut for two-digit multiplications where one number is a multiple of ten (such as 24 x 30 or 98 x 60),

I explain how to multiply by a two-digit number (standard multiplication algorithm). This involves two separate multiplications and lastly adding their results. In the second multiplication, one has to add a zero in the ones place. This is because we're actually multiplying by a multiple of ten (such as 70 or 40). (I explain that more in this video: ) See also my other math videos for 4th grade at

I explain how to multiply by a two-digit number (standard multiplication algorithm). This involves two separate multiplications and lastly adding their results. In the second multiplication, one has to add a zero in the ones place. This is because we're actually multiplying by a multiple of ten (such as 70 or 40). (I explain that more in this video: ) See also my other math videos for 4th grade at

I show a shortcut for 2-digit multiplication problems when one of the factors is a multiple of ten, such as 78 x 50. In such cases the answer is the same as 78 x 5 with a zero tagged to the end. We can write that zero first, and then multiply as if we were multiplying 5 x 78. (Of course this same shortcut works also if one of the factors is a multiple of 100 or 1000 etc.) The lesson also includes one word problem involving area and a calculation where we need to consider the order of operations. The lesson is meant for 4th grade math. See also my other videos for 4th grade at

I show a shortcut for 2-digit multiplication problems when one of the factors is a multiple of ten, such as 78 x 50. In such cases the answer is the same as 78 x 5 with a zero tagged to the end. We can write that zero first, and then multiply as if we were multiplying 5 x 78. (Of course this same shortcut works also if one of the factors is a multiple of 100 or 1000 etc.) The lesson also includes one word problem involving area and a calculation where we need to consider the order of operations. The lesson is meant for 4th grade math. See also my other videos for 4th grade at

In the first problem, we can round the price $11.95 up to $12, which is just five cents more than the real price. Then, to find the price of four items, we can go 4 x $12 = $48, which is 4 x 5 cents too much... so the real total is $47.80. The question is asking for change from $50, which is now easy to figure out by adding up (mental math). In the second problem, we find out how many $0.80 cookies you can get with $20. It turns out, instead of using division, it's easier to use multiplication and mental math to find the answer. This lesson is intended for 4th grade in my Math Mammoth curriculum, but it's also good for older students who don't know these techniques/strategies.

In the first problem, we can round the price $11.95 up to $12, which is just five cents more than the real price. Then, to find the price of four items, we can go 4 x $12 = $48, which is 4 x 5 cents too much... so the real total is $47.80. The question is asking for change from $50, which is now easy to figure out by adding up (mental math). In the second problem, we find out how many $0.80 cookies you can get with $20. It turns out, instead of using division, it's easier to use multiplication and mental math to find the answer. This lesson is intended for 4th grade in my Math Mammoth curriculum, but it's also good for older students who don't know these techniques/strategies.