27.It is given that boat Y and Z are travelling towards each other, the speed of both boats are given.
Y is 35mph and Z is 40mph.
Both boats are 600 miles apart. This can be understood by schematic below:
At the meeting point, the time will be same.
It is known that:
[tex]\begin{gathered} \text{ Speed= Distance/time} \\ \text{time}=\text{ Distance/Speed} \end{gathered}[/tex]Let the Distance travelled by Boat Y be Dy and distance travelled by boat Z be Dz, so it follows:
[tex]\begin{gathered} \frac{D_y}{35}=\frac{D_z}{40} \\ \frac{D_y}{D_z}=\frac{35}{40}=\frac{7}{8} \end{gathered}[/tex]Since Dy+Dz=600, so it follows:
[tex]\begin{gathered} D_z+\frac{7}{8}D_z=600 \\ \frac{15}{8}D_z=600 \\ D_z=320\text{ miles} \end{gathered}[/tex]So the time is given by:
[tex]t_z=t_y=\frac{D_z}{40}=\frac{320}{40}=8\text{ hours.}[/tex]So they meet in 8 hours. Option B is correct.
28. As already calculated that Z will travel 320 miles, so Y will travel 280 miles.
Option D is correct.