Some addition problems are easier than others. The sum of 20 and 32, for example, is easy because it is straightforward: add the tens (2 + 3), and then the ones (0 + 2), to arrive at 52.
Adding 18 and 34, however, results in too many ones to use the same strategy. We can make this sum easier by moving things around a bit.
Step by step | Addition by equivalent sums
- Identify the number that is closer to a ten.
- Add or subtract to make this number into the ten.
- Add or subtract from the other number to maintain the same total value.
- Add the new numbers to find an equivalent sum.
Example | Addition by equivalent sums
Q: 18 + 34
A: The sum of 18 and 34 would be easier if we add 2 to 18 to make 20. Since
we add 2 to 18, we must subtract 2 from 34 to maintain same total value:
18 + 34 = 20 + 32 = 52.