Cost price ,selling price and profit

Find the SP.if cost price is=120 and profit=25%

ans: 

step 1: convert the profit into fractions= 25/100=1/4

step 2:  

           CP    +  Profit =    SP

          4         +   1      =5   (this is by the ratio that you got on step1)

  

(main logic behind is convert any problem into a fraction to solve it quickly. ie scale it down  )

now observer the ratio between actual  CP  and ratio CP(step 2) 

120/4 =30 hence this ratio holds good.

therefore multiply 30 with 1( ratio profit)  =30

              multiply 30 with 5(ratio SP )       =5*30=150