用英语答数学题

1 How can you make 6 out of three 7's ?
2 How can you make 6 out of three 5's ?
3 How can you make 1,000 out of eight 8's ?
4 when do 2 and 2 make more than 4's ?
5 An elephant before two elephants,an elephant behind two elephants,an elephant between two elephants.How many elephants?
1 How can you make 6 out of three 7's ?
7-7/7=6

2 How can you make 6 out of three 5's ?
5+5/5=6!

3 How can you make 1,000 out of eight 8's ?
8+8+8+8+88+888=1000!

4 when do 2 and 2 make more than 4's ?
Answer:When you are wrong!

5 An elephant before two elephants,an elephant behind two elephants,an elephant between two elephants.How many elephants?
Answer:There are 4 elephants.
1.The sum of n different natural numbers is less than50.the greatest possible value of n is----
2.Let a be the average of all odd prime numbers less than 50.The inreger,most close to a is----
3.If two even natural numbers x,y satisfy equation x的平方加100等于y的平方,x大于y then x乘y等于----
1. Since there are some controversies, I suppose 0 does not belong to natural numbers in this case. The answer is quite straight foward, 1+2+3+4+5+6+7+8+9=45. If we add 10, then the sum will exceed 50. So the greatest possible n is 9.

2. First of all, you can list all the odd prime numbers less than 50:3 5 7 11 13 17 19 23 29 31 37 41 43 47. Add them up, and calculate the average. The average a is equal to 23.3. Therefore the integer, most close to a is 23.

3. x^2+100=y^2,then (y-x)(x+y)=100, since x and y are natural numbers, x+y>0, y should be larger than x. I am afraid there is either something wrong with the problem or a typing mistake.
You can show me the original version of the problem 3.

The principal of a new elementary school sounded the alarm for fire training. It took a very long time to empty the building. It was evident that the schoolchildren were at risk. The school has three exterior doors. The main door is served by a wide corridor, the side door by a narrower corridor, and the rear door by a dog-legged corridor.

By experimenting with the classrooms adjacent to each of these doors, it was determined that:

About 1.5 minutes elapse between the announcement of an emergency and the first departure through each door.

Students and staff can file through the doors at these rates approximately 55 per minute through the main door, 30 per minute through the side door, and 25 per minute through the rear door.

About 450 persons are inside the building.
Calculate for the problem the minimum time until the building empties
a.4.1
b.1.5
c.5.3
d.5.6
e.8.18

answer:D

去看看GRE的数学吧