JAMB - Mathematics (1979 - No. 24)
On each market day Mrs. Bassey walks to the market from her home at a steady speed. This journey normally takes her 2 hours to complete. She finds, however, that by increasing her usual speed by 1 km/hr she can save 20 minutes. Find her usual speed in km/hr
1\(\frac{2}{3}\)
2
5
6
10
Giải thích
Let x rep. the usual speed = \(\frac{Distance}{Time}\)
x = d/2
d = 2x ............. 1
x + 1 = \(\frac{d}{2 - 1/3}\)
x + 1 = \(\frac{3d}{5}\)
5x + 5 = 3d
d = \(\frac{5x + 5}{3}\) ................... 2
2x = \(\frac{5x + 5}{3}\)
6x = 5x + 5
x = 5km/hr