WAEC - Mathematics (1999 - No. 28)
A car travel at x km per hour for 1 hour and at y km per hour for 2 hours. Find its average speed
\(\frac{2x + 2y}{3}kmh^{-1}\)
\(\frac{x + y}{3}kmh^{-1}\)
\(\frac{x + 2y}{3}kmh^{-1}\)
\(\frac{2x + y}{3}kmh^{-1}\)
설명
Travelled x km/h for 1 hour \(\therefore\) traveled x km in the first hour.
Traveled y km/h for 2 hours \(\therefore\) traveled 2y km in the next 2 hours.
Average speed = \(\frac{x + 2y}{1 + 2}\)
= \(\frac{x + 2y}{3} kmh^{-1}\)