If he does three hours, its 9 strips, for four, its 12, six is 18, seven is 21, and nine is 27
The answer is actually d lol the idiot above me was right
Answer:

Step-by-step explanation:
we know that
The formula of law of cosines is equal to

where
a, b and c are sides. C is the angle opposite side c
In this problem we have

substitute the given values






5*6=30
and 6*5=30
basically we have to take Lcm of 5 and 6=30
30th day they both will be together