TRICK TO DO % CALCULATIONS

tricks to do % calculations 

calculate the below:
1> what is 23% of 250 ?
ans:  
we can write the above like this also
250 % of 23
so we can do like below
250 % is nothing but     100% + 100% + 50%  
so 100% of 23 is 23
23+23+50% of 23
=>
23+23+11.5=57.5.