RRB NTPC Mains or Stage 2 Model Paper 8 with solutions

Question : 36 of 120

Marks: +1, -0

Three fill pipes A, B and C can fill separately a cistern in 3, 4 and 6 minutes respectively. A was opened first. After 1 minute, B was opened and after 2 minutes from the start of A, C was also opened. Find the time when the cistern will be full?

$2 1/9$ min
$4 1/2$ min
$3 3/4$ min
None of these

Validate

Solution:

(a) Let cistern will be full in x min. Then,part filled by A in x min + part filled by B in(x – 1) min + part filled by C in (x – 2) min = 1

⇒x/3+{x-1}/4+{x-2}/6=1

⇒9x =19 ⇒x 19/9= 21/9

min

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