Answer:
2.40 hours or 2 hours and 40 minutes
Explanation:
If Brian paint a fence in 4 hours, then Brian would paint 1/4 of a fence in 1 hour
And if Scott paint the fence in 6 hours then Scott would do 1/6 of the fence in 1 hour.
Then These two fellows wil pain in 1 hour time
1/4 + 1/6 = ( 3 + 2 ) / 12 = 5 / 12
Then by rule of three and taken into account that 12/12 is the unit we can express:
If both guys paint 5/12 of the fence in 1 hour how long would they take to paint the missing part ( 7/12 ), and add one hour to get the final result
1 hour ⇒ 5/12
x ?? ⇒ 7/12
Then x = ( 7 / 12) / ( 5 /12) ⇒ x = 7/5 hours
x = 1.40 or 1 hour and 40 minutes
Then to paint the whole fence Brian and Scott will take 2.40 hours