Number and Operations in Base Ten
Multiplying and dividing larger numbers
Multiply by a two-digit number, divide with a remainder, and multiply or divide by 10, 100 and 1000.
A two-digit multiplication looks harder than it is. Nobody works out 23 × 14 in one go — you break the 14 into a 10 and a 4, do two easy multiplications, and add them back together.
The rule
Splitting is allowed because 14 lots of something is 10 lots plus 4 lots. You are not changing the question, only doing it in two easier pieces.
Worked example
What is 34 × 12?
Split the 12 into 10 and 2.
Ten is the easiest number to multiply by, so it is worth aiming for one.
Multiplying by 10, 100 and 1000
Every digit slides one column to the left for each zero, so 34 × 100 = 3400. Dividing slides them back the other way. The digits never change, only the columns they stand in.
Try it together
Now let us work out 23 × 14 together.
Same plan as the example: split the second number, multiply twice, add.
1.Split 14 into 10 and 4. Start with the easy half: what is 23 × 10?
Have a go
Have a go on your own: 32 × 13 = ?
Hint: Split the 13 into a 10 and a 3.
Ready to practice?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.