GMATprep 里的两道题...实在不懂

上网的蚊子

1.If Bob produces 36 or fewer in a week, he is paid X dollars per item.  If Bob produces more than 36 items, he is paid X dollars per item for the first 36 items, and 3/2 times that amout for each additional item.  How many items did Bob produce last week?

(1) Last week Bob was paid total of $480 for the items that he produced that week.

(2) This week produced 2 items mor than last week and was paid a total of $510 for the item that he produced this week

key:E

2. When a certain tree was first planted, it was 4 feet tall, and the height of the tree increased by a constant amount each year for the next 6 years. At the end of the 6th year, the tree was 1/5 taller than it was at the end of 4th year. By how many feet did the height of the tree increase each year?

3/10

2/5

1/2

2/3

6/5

第一题为什么不选C? 第二题不明白怎么算的

49hibbert

设 THE TREE INCREASE X FEET EACH YEAR

4+6x-（4+4x）/ 4+4x = 1/5

10x = 4+ 4x

x= 2/3

leaff

以下是引用上网的蚊子在2006-3-12 3:38:00的发言：

第一题为什么不选C? 第二题不明白怎么算的

第一题把条件1和条件2都用上, 答案可能是32个或44个, 不能确定, 所以选E

上网的蚊子

以下是引用49hibbert在2006-3-12 4:42:00的发言：

设 THE TREE INCREASE X FEET EACH YEAR

4+6x-（4+4x）/ 4+4x = 1/5

10x = 4+ 4x

x= 2/3

哦, 1/5不是feet.

谢谢啊

上网的蚊子

以下是引用leaff在2006-3-12 4:58:00的发言：

第一题把条件1和条件2都用上, 答案可能是32个或44个, 不能确定, 所以选E

谢谢哦..有考虑到<36的情况,但不知道为什么脑子里会设定上个星期做了34, 34*15不等于480就把它给排除掉了

郁闷...做题怎么都这么晕晕的

shamoguzhou

1.If Bob produces 36 or fewer in a week, he is paid X dollars per item.  If Bob produces more than 36 items, he is paid X dollars per item for the first 36 items, and 3/2 times that amout for each additional item.  How many items did Bob produce last week?

(1) Last week Bob was paid total of $480 for the items that he produced that week.

(2) This week produced 2 items mor than last week and was paid a total of $510 for the item that he produced this week

key:E

可以列一下式子吗?谢谢.

上网的蚊子

当上星期B生产小于36个时

2X=30

个数=480/15=32

当上星期B生产大于或等于36个

2*3/2*X=30

多出36的个数=(480-36*10)/20=6

总=36+6=42

solartop

春天来了，蚊子都想明白了