问OG12上的problem solving题

橘树

有几题大家帮忙看一下！谢谢啦~

P274 14题这句话看太不懂：Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and drove off the bridge exactly 2 seconds after Y drove off the bridge.

P274 18题what is the maximum number of rectangular blocks,each with dimensions 12 centimeters by 6 centimeters by 4 centimeters,that will fit inside rectangular Box X?

(1)when Box X is filled with the blocks and rests on a certain side, there are 25 blocks in the bottom layer. 说实话这个(1)的答案我看得不太懂，你们能不能帮我看看啊！

P274 23题 the profit from the sale of a certain applicance increases,though not proportionally,with the number of units sold.did the profit exceed $4 million on sales of 380,000 units?

(1)The profit exceed $2 million on sales of 200,000 units.

(2)The profit exceed $5 million on sales of 350,000 units.

P279第70题 Mary persuaded n friends to donate $500 each to her election campaign,and then each of these n friends persuaded n more people to donate $500 each to Mary's campagin. If on one donated more than once and if there were no other donations,what was the value of n? 

答案(2)中 500（n²+n）=120000

n²怎么算的？什么意思？

                                                               谢谢大家进来帮忙解答！

橘树

没人回答？=*=

橘树圣诞节

没人？回答？

橘树圣诞节

第一个和最后一个我已经会了，中间两题，谁帮我看一下！

谢谢了！

pieces6666

第二题是不是说将小长方体放进BOX X 时 , 底层可以放25个，但是放几层不知道，所以not sufficient.

第三题是说profit随销售的量增长，但不成比例，　（２）３５００００　时已经大于4M,