3(b)

Asked by rdk_kulkarni | 7th Sep, 2020, 05:11: PM

Expert Answer:

To find the sum of 17 terms of an AP whose middle term is 40.
 
Let space straight a minus 8 straight d comma space straight a minus 7 straight d comma space straight a minus 6 straight d comma space straight a minus 5 straight d comma space straight a minus 4 straight d comma space straight a minus 3 straight d comma space straight a minus 2 straight d comma space straight a minus straight d comma space straight a comma space straight a plus straight d comma space straight a plus 2 straight d comma
space space space space space space straight a plus 3 straight d comma space straight a plus 4 straight d comma space straight a plus 5 straight d comma space straight a plus 6 straight d comma space straight a plus 7 straight d comma space straight a plus 8 straight d space be space the space 17 space terms space in space AP.
Middlemost space term space is space 40
So comma space straight a space equals space 40

Sum space of space all space terms space is
equals space straight a minus 8 straight d space plus space straight a minus 7 straight d space plus space straight a minus 6 straight d space plus space straight a minus 5 straight d space plus space straight a minus 4 straight d space plus space straight a minus 3 straight d space plus space straight a minus 2 straight d space plus space straight a minus straight d space plus space straight a space plus space straight a plus straight d space plus space straight a plus 2 straight d space plus space
space space space space straight a plus 3 straight d space plus space straight a plus 4 straight d space plus space straight a plus 5 straight d space plus space straight a plus 6 straight d space plus space straight a plus 7 straight d space plus space straight a plus 8 straight d
equals 17 straight a
equals 680

Sum space of space 17 space space terms space is space 680.

Answered by Renu Varma | 8th Sep, 2020, 10:50: AM