87 take away 40 equals what?
We need to find the number that is 40 less than 87. Let’s start with the number 87. How do we make 87? We can make it out of eight tens, that’s the same as 80, and also seven ones, that’s the same as seven. We can model this using a place value grid. Eight tens plus seven ones gives us 87. This is the number we start with.
We now need to take away 40. 40 is made up of four tens. There are also zero ones. So we don’t need to worry about the ones. We just need to take away four tens. We have eight tens. And we need to take away four tens. One, two, three, four. We started with eight tens. We took away four tens. And now we have four tens left because four add four equals eight. And we still have seven ones. And four tens plus seven ones equals 47. By taking away a number of tens from a two-digit number, we don’t need to worry about the ones. The tens digit is the only thing that changes.
87 take away 40 equals 47.