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Question
A car travels with speed 30 km h-1 for 30 minute and then with speed 40 km h-1 for one hour.
Find :
(a) the total distance travelled by the car
(b) the total time of travel, and
(c) the average speed of car
Solution
Speed of car for first 30 minutes = 30 km h-1
Speed of car for next 1 hour = 40 km h-1
(a) Total distance travelled by the car
1st case , Speed =`" Distance "/" Time"`
⇒ Distance = `"Speed" xx "Time"`
(∵ 30 minutes = 0.5 hours)
Distance = `30 xx 0.5`
= 15 km ...........(1)
In second case Speed = `"Distance"/"Time"`
⇒ `"Distance" = "Speed" xx "Time"`
Distance = `40 "km h"^-1 xx 1 "hr"`
= 40 km ............(2)
Adding (1) and (2)
Total Distance = 15 km + 40 km = 55 km
(b) Total time of travel = 0.5 hr + 1.0 hrs = 1.5 hr
(c) Average speed =`"Total distance travelled"/" Total time taken"`
= `(55 "km")/ (1.5 "hr")` [Form above (a) and (b)]
= 36.67 km h-1
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