Question

16.
The cost of manufacturing a commodity
increased by 20%. A trader who did not revise
the selling price noted that there was a drop
of Rs.20 in his profit. What was the original
cost price?
(1) Rs.100 (2) Rs.200 (3) Rs.500
(4) Rs. 150 (5) None of these​

Answer 1

Answer:

100 rupees

Option A is correct....

Answer 2

The Original Cost Price is 100 Rs

Given:

Increase in cost price = 20%

decrease in profit = 20 Rs

Selling Price is unchanged

To Find:

The original cost price

Solution:

Lets denote original cost price by  CP

Lets denote selling price by SP

Lets denote profit by P

The current cost price is increase in original cost price by 20%

= CP + 20/100 CP

=1.20 CP

Profit = selling price - original cost price

P = SP - CP

so SP = CP + P

Due to increase in manufacturing we now have 20 Rs drop in profit

Profit -20 = Selling Price - current cost price

P - 20= SP - 1.20 CP

Replacing SP by CP + P we have

P - 20 = (CP + P) - 1.20 CP

P - 20 = CP + P - 1.20 CP

P - 20 = P +( CP - 1.20 CP)

P - 20 - P = -0.2 CP

-20 = - 0.2 CP

CP = 20/0.2

     = 100 Rs

So the Original Cost Price is 100 Rs

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