SAT Question 623dbebb: Percentages answer and explanation with Desmos solution

05$.I{t}^{\prime }sgiventhatthepurchasepriceforcertainbooksis＄5.00$ dollars each. It's also given that each book is marked for sale at a consumer price that is ＄270 %$ofthepurchaseprice.Sincetheconsumerpriceis＄270\%$ of the purchase price of ＄5.00$dollars,itfollowsthattheconsumerpriceis$( 2.7 ) ( 5.00 )$,or＄13.50$, dollars. It's given that after ＄4$months,anyremainingbooksarediscountedat＄70\%$ off the consumer price. Thus, the discount amount is $(0.7)(13.50)$, or ＄9.45$,dollars.Subtractingthediscountamountfromtheconsumerpricegivesthediscountedpriceofeachoftheremainingbooks:＄13.50-9.45=4.05$. Note that 81/20, 4.05, and 4.050 are examples of ways to enter a correct answer.