Answer:
2.4 hours
Step-by-step explanation:
David's time = 6 hours
Anthony's time = 4 hours
the combined time is given by the following formula
1/ (david's time) + 1/(anthony's time) = 1/total time
1/6 + 1/4 = 1/Total
4/24 + 6/24 = 1/Total
10/24 = 1/ total (taking reciprocal of both sides)
24/10 = total
total time = 24/10 = 2.4 hours
I think maybe either B or C, ope I helped, sorry if I didn't!!
1) 0.4
2)0.875
i dont know the 3 and 4 one
