If the 3 numbers whose average is 40, the first is \frac{1}{3} rd the sum of other 2 . What is the first number?

BA LLB Banaras Hindu University 2018 Solved Paper

Question : 115 of 170

Marks: +1, -0

If the 3 numbers whose average is 40, the first is

\;{1}/{3}

rd the sum of other 2 .
What is the first number?

Solution:

Let the numbers be

x, y

and

z

Now, average

=\;{x+y+z}/{3}=40

⇒ \;\; x+y+z=120

......(i)
and

x=\;{1}/{3}(y+z)

⇒ \;\; 3 x=y+z

.....(ii)
Using Eqs. (i) and (ii), we get

x+3 x \;\; =120

⇒ 4 x \;\; =120

∴ x \;\; =30

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