Excel cell number auto fill

[Tangy123]

Hi,

Kindly assist me with the formula excel use to calculate a figure when you highlight more than one cell with numbers, and drag it, you get an auto calculated number, example Cell: B1,C1, and D1 have figures of 443, 432, and 571 respectively, if you highlight those three cells, then drag to Cell E1, the figure is calculated to 610.  Kindly assist with what formula is used to get 610.

Thank you for your assists in advance

[#2]

@Tangy123 

Excel uses linear extrapolation: it calculates the straight line that best fits these values:

You can return the value 610 using the formula =TREND(B1:D1,{1,2,3},4)

[#3]

Thank you very much