Question

Can someone please help me on this problem? I need help on it please!!

Answer 1

60 m/h

Explanation:

1. the basic formula is Time=Distance/Speed;

2. total time is time1 (for 84 miles)+time2 (for 130 miles)=time (4 hours);

3. the time for the first 84 mi. is time1=84/S;

4. the time for the rest 130 mi. is time2=130/(S-10);

5. using all the data of items 2-4, it is possible to substitute into the basic formula and resolve an equation:

`(84)/(s) +(130)/(s-10) =4; \ => \ 2s^2-127s+420=0;`

`\left[\begin{array}{ccc}s=60\\s=3.5\end{array}`

note, that the value of speed has one condition: s>10. It means, the only value is true: 60 miles per hour.