Miscellaneous Question 48
- The respective ratio of time taken by inlets $A$ and that by inlet $B$ to fill an empty tank is $3: 4$. When the tank was fully empty, inlet A and inlet B were opened alternately (A in the 1st hour, B in the 2nd, A in the 3rd ….). At the end of $12$ hrs, if $70 \%$ of the tank was full, in how many hours can inlet A (alone) fill the empty tank completely?
(1) $15$ hrs
(2) $9$ hrs
(3) $20$ hrs
(4) $12$ hrs
(5) None of those given as options
(IBPS RRBs Officer CWE (Prelim Exam) 11.08.2018)
Show Answer
Correct Answer: 48. (1)
Solution: 48. (1) Time taken by tap A $=3 x$ hours.
Time taken by tap B $=4 x$ hours
Part of tank filled in first two hours $=\frac{1}{3 x}+\frac{1}{4 x}$
$=\frac{4+3}{12 x}=\frac{7}{12 x}$
Part of tank filled first 12 hours
$=\frac{6 \times 7}{12 x}=\frac{7}{2 x}$
$\therefore \frac{7}{2 x}=\frac{7}{10} \Rightarrow x=5$
$\therefore$ Time taken by tap A $=15$ hours
BETA
