Question 6220

a) 30%
b) 23.5%



If the marked price is x, then the sp = 0.9x 
We don’t know the cost price, so cp = y

If the profit is 17%, then 

P = Sp – Cp
         Cp
0.17 = 0.9 x – y
               y
0.17 = 0.9 x – 1
             y
1.17 =  0.9x   ______________ (1) this is the key step 
              y 

Now, if it is sold at the marked price, then we know
Profit = Sp – Cp     =   x - y  =  x – 1 
               Cp                   y          y
And if you substitute the value of y from (1), you will find that 
  Profit =    x   -   1  = 0.3 or 30%
               0.9x
               1.17

similarly, answer to (b) should be 23.5%