12. Looking at decimal representation of a number how can we determine whether the number is rational or irrat?

Just see whether the digit after decimal point repeats or not example-suppose the no is 1.012340123 you will see here that 01234 repeats and will reapeat again and again so this is rational no. since the decimal is repeating. A irrational number is non terminating non recurring.Ex-1.010010001 in this example their is no chance of repeatetion so the no. is irrational.