work done by A in 1 hour = \(\frac{1}{10}\)
work done by B in 1 hour = \(\frac{1}{6}\)
work done by A and B in 1 hour = \(\frac{1}{10}\) + \(\frac{1}{6}\)
= \(\frac{16}{60}\)
They worked together for 3 hours. So \(3*\frac{16}{60}\)
\(\frac{16}{20}\)
Remaining work is \(\frac{4}{20}\)
Now A stopped working and B has to complete the work.
\(x*\frac{1}{6}\) = \(\frac{4}{20}\)
x = \(\frac{24}{20}\)
x = \(\frac{24}{20}*60\) minutes
x = 72 minutes or 1 hour 12 minutes.
OPTION:
B
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Regards,
Chaitanya
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