Explanation:

From the given data,

When the price of rice is decreased by 10%, the value of Rs. 270 would become

270 x 100/90 = 300

Now, the value 270 becomes 300

And given, the girl could buy 1 kg extra for that value

Change in value = 300 - 270 = Rs. 30

Therefore, 1 kg extra rice she can get for Rs. 30

= The original price of rice = Rs. 30/kg.

As she gets only 9 kgs for Rs. 270 before 10% discount,

now after discount she gets 10 kgs instead of 9 kgs for Rs. 270.

Hence, option 1 is the correct answer.