Please help me solve this problem its in the more detail spot

crawford can paint a fence by himself in 15 hours and bernice can paint the same fence in 16 hours. How long will it take them to paint the fence if they work together?

Divide the two in half, and find the average of those two.
7.5, 8
*7.75*

OR

(1/16 + 1/15)x = 1

Find x

(31/240)x = 1

*7.5*

Portion of the fence that Crawford can paint in x hours = x/15
Portion of the fence that Bernice can paint in x hours = x/16

Working together

(Crawford's part) + (Bernice's part) = 1

x/15 + x/16 = 1

and solve for x.

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fast way for competitions

use the parallel work formula

15*16/(15+16)

Depends on how big the fence is.Right?