Math, asked by sagarraviprata, 1 year ago

The sum of four numbers in GP is 60 and the a.m. of the first and the last is 18 the numbers are

Answers

Answered by SaiSoumya
46

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Answered by wifilethbridge
35

Answer:

Let the four terms of Gp be a,ar,ar^2,ar^3

The sum of four numbers in GP is 60

So,a+ar+ar^2+ar^3=60 ---A

We are given that  the a.m. of the first and the last is 18

So,\frac{a+ar^3}{2}=18

a+ar^3=36 --B

Substitute the value in A

36+ar+ar^2=60

ar+ar^2=60-36=24 ---C

Divide B and C

\frac{a+ar^3}{ar+ar^2}=\frac{36}{24}

\frac{1+r^3}{r+r^2}=\frac{36}{24}

2r^3-3r^2-3r+2=0

r=-1,\frac{1}{2},2

So, at r = 1/2

a(1+\frac{1}{2}^3)=36

a=32

a,ar,ar^2,ar^3=32,16,8,4

At r = 2

a(1+2^3)=36

a=2

a,ar,ar^2,ar^3=32,64,128,256

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