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Posted by on Wednesday, January 9, 2013 at 1:45am.

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

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

  • Math - , Wednesday, January 9, 2013 at 4:59am

    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.

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