sky wrote:

If the price of a magazine is to be doubled, by what percent will the number of magazines sold decrease?

(1) The current price of the magazine is $1.00.

(2) For every $0.25 of increase in price, the number of magazines sold will decrease by 10 percent of the number sold at the current price.

The answer is straightforward here. The question stem is asking for the percentage difference in the sales of magazines due to the increase in price. To calculate the percentage difference in the no. of sales of magazines due to the increse in price, we require two parameters. Current Price and impact on sales due to the fluctuation in price.

1. It gives the information about only one parameter, Current price - Not sufficient

2. It brings more light into the direct relationship b/w changes in price and no. of magazines sold. - Not sufficient

1+2 -> We know the current price and also have the information about the decrese isn sales due to an increase in the price. Hence, sufficient.