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Of the three numbers, the first is twice the second and the second is twice the third. The average of the reciprocal of the numbers is (dfrac{7}{72}) .The numbers are:


16, 8, 4


20, 10, 5


24, 12, 6


36, 18, 9

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Option(C) is correct

Let three numbers be $x, y,z$

Given $x=2y⇒x=4z;y=2z;z=z$

The average of reciprocal numbers is \(\dfrac{7}{72}\)







$⇒x=4×6$ = 24

(3) Comment(s)

Sri Devi

yes...verification through options is the quickest method. however, if anyone wants any other alternative, here is one: :)

f=2s => s=(f/2) ..... (i)

s=2t => t=(s/2) ..... (ii)

(i) & (ii) clearly show that f, f/2, f/4 are the required numbers :)


((1/f)+(2/f)+(4/f))/3=(7/72) (given that avg of reciprocals is 7/72)

7/f = 7/24 => f=24

there is no need to determine the rest of the two numbers as there is only one option with 24 as one of the numbers :)



3rd no=1

2nd no=2

1st no= 4

now according to question

=>(1/4x+1/2x/+1/x)/3= 7/72

=>(1+2+4)/4x= 7/24



now it can be said that 3rd no is 6 2nd is 12 and 1st is 24.


This is the type of question which can also be simply & fast solve through options.