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.
benchmark numbers
Compatible number
It depends on your computational skills.
compatible numbers
Compatible Numbers numbers that are easy to compute mentally are called
No.
Your brain, of course.
easy to divide mentally
Compatible numbers can easily be divided mentally.
Compatible numbers can easily be divided mentally.
Rational?
The patterns and properties to compute mentally 120 times 30 is the numbers 12 and 3 plus the two 0. Multiply 12 by 3 (36) and add the two 0 (3600).