Find the two numbers from 10, 20, 60, and zero which add up to 30.
We have been given a list of four numbers. We can only use two of them. And we need to add them together to get 30. Almost immediately, we can recognize one of these numbers we won’t be able to use. We won’t be able to use the number 60 because it is already larger than 30. That leaves us with the numbers 10, 20, and zero.
Can I use the number zero? Well, I know that zero plus 30 equals 30. But our list of numbers doesn’t include 30. And that tells me that I also can’t use zero from this list.
Now we’re only left with two choices, 10 and 20. Now we need to check and see if 10 plus 20 equals 30. If we’re adding 10 plus 20, we first add the ones place. Zero plus zero equals zero. After that, we move on to the tens place. One plus two equals three. So yes, 10 plus 20 does equal 30. From our list of four numbers, we would choose the numbers 10 and 20.