The difference between mental math, rounding, and estimating is:

• Mental Math: This is when you solve math problems in your head without writing anything down or using a calculator. For example, if someone asks you what 8 + 7 is, you can think about it and quickly say, "15!" That's mental math!

• Rounding: Rounding means changing a number to a nearby, simpler number to make it easier to work with. For example, if you have the number 48, you can round it to 50 because 50 is easier to think about. You use rounding when the number is close to something that ends in 0.

• Estimating: Estimating is when you make a good guess about an answer that doesn't have to be exact. You can use rounding to help you estimate. For example, if you’re adding 48 + 32, you might round them to 50 and 30, and then you can estimate that the sum is about 80.

So, mental math is solving in your head, rounding is making numbers easier, and estimating is making a good guess at the answer!