Find the 20th term of the series 2.4+4.6+6.8+........
kvnmurty:
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
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Answered by
5
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
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
Answered by
1
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
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
thnx very much
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