In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data
bike price = 644.80 rupees
gain = 4% = 0.04
cp = cost price = ?
Step 02:
cost price = bike price - bike price*gain
= 644.80 rupees - 644.80 rupees * 0.04
= 644.80 rupees - 25.729 rupees
= 619 rupees
The answer is:
The cost price is 619 rupees.
