Multiplying two two-digit numbers
In 4th grade, children learn to multiply two two-digit numbers, such as 64 × 38, by splitting each one into tens and ones and adding the four smaller products.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 4th grade practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
A can of paint costs $15. A school buys 13 cans. How much does the paint cost?
- $195
- $115
- $150
Why this matters
This is where your child’s times tables go to work on bigger pairs, like 38 rows of 64 seats or a room 12 feet by 14. Next year it supports dividing by two-digit numbers, and in algebra the same splitting into parts is used to multiply expressions with letters in them. At home, it is how you would price 12 pizzas at $15 each.
If breaking one number apart by place value is still new, your child can start with multiplying large numbers by a one-digit number.
Where kids can get stuck
- Multiplying only the matching places, so 64 × 38 becomes 1,800 + 32 = 1,832, missing 60 × 8 and 4 × 30.
- Treating tens as ones inside a part, writing 60 × 30 as 180 instead of 1,800.
- Getting each part right but adding them wrongly, such as lining up 1,800, 480, 120, and 32 by their left edges.
How you can help
- Work out a real cost together, like 24 tickets at $13 each. Have your child split it as 20 × 13 and 4 × 13, then add 260 and 52 to get $312.
- Draw a rectangle on a paper napkin and label its sides 23 and 15. Ask your child to cut it into four boxes by tens and ones and find each box before adding.
- Count something big in the house, such as tiles on a floor that is 12 tiles by 18 tiles. Let your child estimate first, then multiply by parts and compare with the estimate.
For more, Bobby's Math Club has free practice at your child’s level.
Questions parents ask
Why is my child drawing boxes to multiply?
The boxes, often called an area model, show every part of the multiplication. For 64 × 38, a rectangle split into tens and ones gives four boxes: 60 × 30 = 1,800, 60 × 8 = 480, 4 × 30 = 120, and 4 × 8 = 32. Adding them gives 2,432. Because each part has its own box, your child can see why there are four, and a missing one stands out.
Can I teach my child the method I learned?
You can show it, but it helps to connect it to what your child is doing in class. The stacked method does the same four multiplications, and your child will learn it in 5th grade. Try working one problem both ways side by side and finding the matching pieces. For 64 × 38, the row for 8 holds 480 + 32 = 512, and the row for 30 holds 1,800 + 120 = 1,920.
What if my child can multiply by one digit but finds two-digit numbers harder?
That’s a common jump, and it doesn’t mean anything is wrong. Now both numbers are split, so every part of one has to meet every part of the other, and the tens-times-tens part is new: 20 × 40 is 800, not 80. Try a problem where one number is a multiple of ten, like 64 × 30, before moving on to 64 × 38.
Make learning math fun
Bobby's Math Club turns 4th grade math practice into something fun to do together.
- Unlimited free practice
- Questions matched to your child’s level, a few minutes a day
- Level-ups, badges, and a cheer for every win
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
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Join the clubNote for teachers: This skill is covered by Common Core math standard 4.NBT.B.5: “Multiply 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.” Learn how Bobby's Math Club can help your students grow. (Common Core 4.NBT.5)