Question

小林在某商店购买商品A，B共三次，只有其中一次购买时，商品A，B同时打折，其余两次均按标价购买，三次购买商品A、B的数量和费用如表所示，                                                                

                                    购买商品A的数量/个　                                   　购买商品B的数量/个     购买总费用/元　

第一次购物                  6                                  5                                  1140

第二次购物                  3                                  7                                  1110

第三次购物                  9                                  8                                  1062

（1）在这三次购物中，第　　　　　　次购物打了折扣；                             

（2）求出商品A、B的标价；                                                                 

（3）若商品A、B的折扣相同，问商店是打几折出售这两种商品的？             

Answer 1

【考点】二元一次方程组的应用．                                                           

【分析】（1）根据图表可得小林以折扣价购买商品A、B是第三次购物；                    

（2）设商品A的标价为x元，商品B的标价为y元，根据图表列出方程组求出x和y的值；                   

（3）设商店是打a折出售这两种商品，根据打折之后购买9个A商品和8个B商品共花费1062元，列出方程求解即可．                                                                         

【解答】解：（1）小林以折扣价购买商品A、B是第三次购物．                    

故答案为：三；                                                                                 

                                                                                                          

（2）设商品A的标价为x元，商品B的标价为y元，                                    

根据题意，得，                                                                

解得：．                                                                               

答：商品A的标价为90元，商品B的标价为120元；                                    

                                                                                                          

（3）设商店是打a折出售这两种商品，                                                  

由题意得，（9×90+8×120）×=1062，                                                 

解得：a=6．                                                                                      

答：商店是打6折出售这两种商品的．                                                    

【点评】本题考查了二元一次方程组和一元一次方程的应用，解答本题的关键是读懂题意，设出未知数，找出合适的等量关系，列方程求解．