Tony alone can paint a wall in 7 days and his friend Roy alone can paint the same wall in 9 days. In how many days they can paint the wall working together? Round off the answer to the nearest integer.  Choose the correct choice from the following choices: A) 2 B) 4 C) 6 D) 7 E) 9
Sol. use formula (xy / x+y)   So nearest value for 3.93 = 4   Answer: Option 4
<result>B</result>
Tony alone can paint a wall in 7 days and his friend Roy alone can paint the same wall in 9 days. In how many days they can paint the wall working together? Round off the answer to the nearest integer.