Answer:
Step-by-step explanation:
Use distance formula:
- d = st, where d- distance, s - speed, t - time
a)
Total distance is:
Solve for x:
- 8x = 70 - 10y
- x = (70 - 10y)/8 = (35 - 5y) / 4
Solve for y:
- 10y = 70 - 8x
- y = (70 - 8x) / 10 = (35 - 4x) / 5
b)
Average speed is:
- s(av) = d / t = 70 / (x + y)
c)
The second scenario:
Combine with the first one and solve the system:
Solve by elimination as below:
- 5(10x + 8y) - 4(8x + 10y) = 5*72 - 4*70
- 50x + 40y - 32x - 40y = 360 - 280
- 18x = 80
- x = 40/9
Find y:
- 10*40/9 + 8y = 72
- 8y = 72 - 400/9
- 8y = 248/9
- y = 31/9
