The sum of the integers from 40 to 60, inclusive, is 1050. what is the sum of the integers from 60 to 80 inclusive?

Question

Please help me find the pattern and how to use it instead of adding 60+61+62+63..... etc.

Answer 1

Use the Gauss method:
60+61+62...+70+71...+80
80+79+78+..+70+69...+60

Add the two lines, you will get the sum 140 21 times. So half the sum is 70*21=1470.