    Question

# Let a1, a2, a3, a4 …….. be an arithmetic progression and g1, g2, g3, g4 …… be a geometric progression. If a1+g1=1, a2+g2=4, a3+g3=15 and a4+g4=2, then

A

the common ratio of geometric progression is equal to –2.

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B

the common ratio of geometric progression is equal to –3

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C

20k=1ak=960

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D

20k=1ak=480

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Solution

## The correct options are B the common ratio of geometric progression is equal to –3 C ∑20k=1ak=960 Let a and d be first term and common difference of A.P. Also, let b and r be the first term and common ratio of G.P. ∴ On solving, we get a=12, b=12, d=5, r=−3Also, ∑20k=1ak=960  Suggest Corrections  0      Similar questions  Related Videos   Arithmetic Progression
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