MENU
Question -

Find three numbers in G.P. whose sum is 65 andwhose product is 3375.



Answer -

Let the three numbersbe a/r, a, ar

So, according to thequestion

a/r + a + ar = 65 тАжequation (1)

a/r ├Ч a ├Ч ar = 3375 тАжequation (2)

From equation (2) weget,

a3┬а=3375

a = 15.

From equation (1) weget,

(a + ar + ar2)/r= 65

a + ar + ar2┬а=65r тАж equation (3)

Substituting a = 15 inequation (3) we get

15 + 15r + 15r2┬а=65r

15r2┬атАУ50r + 15 = 0тАж equation (4)

Dividing equation (4)by 5 we get

3r2┬атАУ10r + 3 = 0

3r2┬атАУ9r тАУ r + 3 = 0

3r(r тАУ 3) тАУ 1(r тАУ 3) =0

r = 3 or r = 1/3

Now, the equation willbe

15/3, 15, 15├Ч3 or

15/(1/3), 15, 15├Ч1/3

So the terms are 5,15, 45 or 45, 15, 5

тИ┤┬аThe threenumbers are 5, 15, 45.

Comment(S)

Show all Coment

Leave a Comment

Free - Previous Years Question Papers
Any questions? Ask us!
×