You have already learned how to find the greatest (larger) number if it is missing in a number family. Now let's now learn how to find the missing lesser (smaller) number.

Remember, we can use a number family to write a subtraction fact. Let's see if you can give a sub­traction fact for this number family:

One subtraction fact for this number family is 6 minus 4 equals 2 (6 - 4 = 2). Did you get it right? The other subtraction fact you might have thought of is 6 minus 2 equals 4 (6 - 2 = 4).

Now, if a number family has a missing lesser number, what are you going to do?

Again, it's simple.­ We always subtract to find the missing lesser number. We start with the greatest number and subtract the lesser number. In number families, the greatest number is always at the end of the arrow.

Look at this number family:

A lesser number is missing. To find it, we go backwards along the arrow. The subtraction problem is 6 minus 4 (6 - 4). What number is missing? The difference (answer) equals 2, so the missing lesser number is 2.

Let's have more practice! Just remember that if a family is missing a lesser number, we always subtract.

Can you find the missing lesser number in this number family?

Go backward along the arrow. Now, the subtraction problem is 8 - 7. Can you find the difference? The answer is 8 minus 7 equals 1 (8 - 7 = 1). The missing lesser number is 1.­