Add 3-digit numbers choosing appropriate mental strategies

Adding three-digit numbers using mental strategies can be a straightforward process, especially when the numbers to be added are in the tens or hundreds place. For instance, when you add 468 and 8, you simply increase the ones digit, resulting in 476. However, if you add 80 to 468, only the tens digit changes, giving you a sum of 548. Similarly, adding 800 to 468 changes only the hundreds digit, resulting in 1268. This pattern is evident across various examples, such as adding 6, 60, or 600 to 532, which yields 538, 592, and 1132, respectively.

Another observation from these exercises is that when adding tens to a three-digit number, as Colin suggests, the ones digit remains unchanged. This is always true and can be demonstrated with practical resources or simple jottings. For example, adding 50 to 364 gives you 414, and adding 60 to 464 results in 524, with the ones digit staying constant in both cases. This principle is a key element in mental arithmetic and helps simplify the process of addition. The exercises also include matching pairs problems and encourage creating one's own missing digit problem to deepen understanding of the concept.