Discussion

Explanation:

For the first increase decrease cycle of +x% and -x%, overall change would be (-x2/100)%. This results in a decrease of 200 and the price becomes P – 200.

The next increase decrease cycle of +x% and -x% would be on a smaller base of (P – 200). The overall change would be the same(-x2/100)%. The absolute change would be (P - 200) × x2/100 which would definitely be less than 200.

Hence, the total change after 2 such cycles would definitely be more than 200 but less than 400. Only option (b) satisfies this criterion.

Alternately,

Let P be the original price of the laptop.

According to the question,

After one cycle, P1+x1001-x100 = P - 200

1+x1001-x100 = P-200P   ...(1)

After second cycle, P1+x10021-x1002 = 19,602

From (1)

(P-200)2P = 19602   ...(2)

⇒ (P – 200)2 – 19602P = 0

⇒ P2 – 20002P + 40000 = 0

⇒ P = 20,000 and 2

P = 2 is not possible.

Hence, P = Rs. 20,000

Hence, option (b).

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