Find the 20th term of the series 2.4+4.6+6.8+........

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you have to put a * if u wanted to say 2 times 4 + 6 times 8... otherwise a . is understood as a decimal
but this same model sum is repeated in our 8th class techno book. our teachers told us in this way
so i done in this way sir
u hav to modify. i asked for correction Bhaghi
ok sir

Answers

2014-10-25T20:01:14+05:30
2.4+4.6+6.8+......... is given
 in this 2 progressions are there
1st- 2+4+6+.......                                     2nd- 4+6+8+.........
 here a = 2 d = a₂-a₁                        here a = 4  d = 6-4
                   = 4-2 = 2                                            = 2
a₂₀ = a+(20-1)2                                    a₂₀ = a +(20-1)2
     = 2+19(2)                                             = 4 + 19(2)
     = 2+38                                                  = 4 + 38
    a₂₀ = 40                                            a₂₀ = 42
a₂₀ of 2.4+4.6+6.8+.........= 40×42
                                       =  1680
0
The Brainliest Answer!
2014-10-25T20:08:55+05:30
A=2.4
d=4.6-2.4=2.2
tn=a+(n-1)d
   =2.4+(n-1)2.2
   =2.4+2.2n-2.2
    =2.2n+0.2
   =2.2(20)+0.2
   =44+0.2
    =44.2
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