10000+10000-20000+1=

10000+10000-20000+1=

one

The railway between Shanghai and Nanjing is about 300 km long. How many hours after departure can the EMU catch up with the ordinary express?

If the EMU can catch the ordinary express train within X hours after departure, 180X = 80x + 300, & nbsp; 180x-80x = 80x + 300-80x, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 100x = 300100x / 100 = 300 / 100, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp

The railway distance between Shanghai and Nanjing is about 300 km. Two motor cars start from Shanghai and Nanjing at the same time and run in opposite directions. One motor car runs every minute on average
The distance between the two trains is 145 km after 2.5 km, and the other train is 3.7 km per minute on average

Setting: after X minutes, the two trains are still 145 kilometers apart
（300-145）=（2.5+3.7）X
X = 25 minutes
After 25 minutes, the two trains are still 145 kilometers apart

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+-----------+10000=?

The sum of the first n terms of the arithmetic sequence is s = n * (n + 1) / 2, and N is the number of terms
In the question, n = 10000,
The formula is s = 10000 * (1000 + 1) / 2 = 5005000