Question

A girl is cycling and she covers $0.5km$ in $2$ minutes, next $0.75km$ in $3$ minutes and last $1$ km in $4$ minutes. Select the options that correctly mention her average speed.

• A. $4.16m{s}^{-1}$
• B. $0.25m{s}^{-1}$
• C. $0.25kmmi{n}^{-1}$
• D. $4.16kmmi{n}^{-1}$

Answer 1

Answer: (A), (C)

The correct options are
A

$4.16m{s}^{-1}$

C

$0.25kmmi{n}^{-1}$

In the first part of the journey, the distance covered = $0.5km$ and time = $2$ minutes
In the second part of the journey, the distance covered = $0.75km$ and time = $3$ minutes
And, In the third part of the journey, the distance covered = $1km$ and time = $4$ minutes
So total distance covered = $2.25km$ and total time = $9$ minutes
So,average speed = $\frac{\text{total distance}}{\text{total time}}$
= $\frac{2.25}{9}=0.25kmmi{n}^{-1}$
And,$1km=1000m$ and $1min=60s$
So average speed in $m{s}^{-1}$ = $\frac{0.25\times 1000}{60}=4.16m{s}^{-1}$