There are two pumps to fill a tank with water. First pump can fill the empty tank in 8 hours, while the second in 10 hours, If both the pumps are opened at the same time and kept open for 4 hours, the part of the tank that will be filled up is :
There are two pumps to fill a tank with water. First pump can fill the empty tank in 8 hours, while the second in 10 hours, If both the pumps are opened at the same time and kept open for 4 hours, the part of the tank that will be filled up is :
[A]$latex \frac{2}{5}&s=1$
[B]$latex \frac{1}{5}&s=1$
[C]$latex \frac{9}{10}&s=1$
[D]$latex \frac{1}{10}&s=1$
$latex \frac{9}{10}&s=1$
Part of the tank filled in an hour by both pumps
$latex = \frac{1}{8}+\frac{1}{10} = \frac{5+4}{40} = \frac{9}{40}&s=1$
∴ Part of the tank filled in 4 hours
$latex = \frac{4\times 9}{40} = \frac{9}{10}&s=1$
Hence option [C] is correct answer.