Question

Find car A and car B speed in km/h

Answer 1

• 72 km/h and 48 km/h

Explanation:

Let the speed of the cars be x and y.

When moving in opposite directions, the speeds add up and when moving in the same direction the speeds subtracted.

Convert time from minutes to hour:

• 4 minutes = 4*1/60 hr = 1/15 hr
• 20 minutes = 20*1/60 hr = 1/3 hr

Opposite direction

• (x + y)*1/15 = 8
• x + y = 8*15
• x + y = 120

Same direction

• (x - y)*1/3 = 8
• x - y = 8*3
• x - y = 24

Add up the two equations and find the value of x:

• x + y + x - y = 120 + 24
• 2x = 144
• x = 72

Find y:

• 72 + y = 120
• y = 120 - 72
• y = 48