Numbers that are easy to compute mentally are called "friendly numbers." These numbers typically have properties that make them easier to work with, such as being multiples of 10 or having a lot of factors. Friendly numbers are often used in mental math strategies to simplify calculations and make them more efficient.
benchmark numbers
easy to divide mentally
one
The difference between compatible numbers and estimation is that in estimation you round to the nearest ten or hundred most of the time. Compatible numbers are numbers that are easy to compute mentally. Some examples of compatible numbers when doing division are 400 and 10, 36 and 6, 2400 and 12, and 64 and 8 2400 and 12 are compatible because when doing this division (2400/12), we can quickly divide 24 by 12 to get 2 and put two zeros at the end to get 200 Some examples of compatible numbers when doing multiplication are 200 and 40, 1100 and 40, 25 and 4. 1100 and 40 are compatible because we can quickly do this multiplication by multipling 11 and 4 to get 44 and add three zeros at the end to get 44000 Hope this helps!
o that's easy....it just means to do the math in your head instead of working it out on paper
benchmark numbers
It depends on your computational skills.
compatible numbers
Numbers like 10, 25, 50, and 100 are easy to compute mentally because they have simple multiples or divisions that are easy to work with. For example, doubling 25 is 50, or dividing 100 by 10 gives you 10. These numbers are often used as benchmarks in mental math calculations.
Your brain, of course.
No, but if you practice you can learn to do it and it gets easier. Start of by learning (by rote) your times tables and when adding up do so in 10s.
easy to divide mentally
Compatible numbers can easily be divided mentally.
Break it up into two separate problems. First 4X25=100, which is easy enough. Then 27X100=2700.
Rational?
one
dont know about associative property but this one is easy in your head. 4x25=100x27=2700