RRB Junior Engineer Stage 1 Model Papers 4

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Question : 26 of 99

Marks: +1, -0

If

a + b + c = 3,a^2+b^2+c^2=6

and

1/a+1/b+1/c=1

, where a, b, c are all non-zero, then 'abc' is equal to

$2/3$
$3/2$
$1/2$
$1/3$

Solution:

a + b + c = 3

Squaring both sides

a^2+ b^2+ c^2+ 2 (ab + bc + ac) = 9

6 + 2 (ab + bc + ca) = 9

ab+bc+ca=3/2

....(1)
given

1/a+1/b+1/c=1

⇒ab+bc+ac=abc=3/2

[from (1) ]

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