Question

If a car travels the first one third of its des
one third of its destination with a uniform sneed 30 km/h and the remaining part at an
of its destination with a uniform speed 10 km/h, second
uniform speed 5 km/h, what is its average speed ?
একটি গাড়ী তার যাত্রা পথের প্রথম এক-তৃতীয়াংশ 10 km/h সম দ্রুতিতে, দ্বিতীয় এক-তৃতীয়াংশ 30.
| km/h সম দ্রুতিতে ও শেষ অংশ 5 km/h সম দুতিতে চললে তার গড় দুতি কত?​

Answer 1

Answer:

12.8 km/hr

Explanation:

let total distance is d

first 1/3rd

v = 30 km/h

d1 = d/3 km                     so t = d / 90

remaining 2/3

v = 10 km/h

d2 = 2d/3            so t = d /15          

second part

v = 5 km /h

d3 = d/3               so t = d /15

v avg = total distance / total time

 

=  d / d/90 + d/15 + (  d/15 - d/15 )

= 1350 / 105 = 12.8 km/hr