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Find three numbers in G.P. whose …

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Find three numbers in G.P. whose sum is 28 and whose product is 512.
  • 2 answers

Ranger King 4 years, 3 months ago

Let the three numbers be a,ar, ar2, where r is the common ratio. ⇒a+ar+ar2=28 and a3r3=512 ⇒ar=8⇒a+ar2=20 ⇒8r2−20r+8=0 ⇒r=2,r=21​ If r=2,a=4 Therefore, the three numbers are 4,8,16

Yogita Ingle 4 years, 3 months ago

The three numbers in GP are 4 , 8 , 16.

  • Let the three numbers in GP be a/r , a , ar.
  • Now the product of three numbers is given as 512.

a/r × a × ar = 512

a³ = 512

a = 8

  • Now sum of the three numbers is given as 28.

a/r + a + ar = 28

8/r + 8 + 8r = 28

8 + 8r² = 20r

8r² - 20r + 8 =0

8r² - 16r - 4r + 8 =0

8r(r-2) - 4(r-2) = 0

(r-2)(8r-4) = 0

  • Therefore, r = 2 or r=1/2
  • Now , the  three numbers are 4,8,16.
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