## Solution:

We know that 1 km=1000 m and 1 hr=3600 sec.

Convert 342 m/s.

$\displaystyle 342\:m/s=\left(342\:\frac{m}{s}\right)\left(\frac{1\:km}{1000\:m}\right)\left(\frac{3600\:s}{1\:hr}\right)=1231.2\:km/hr$          ☚

Therefore, the speed of sound in km/hr is 1231.2 km/hr.

## Solution:

### Part a

$\displaystyle 33\:m/s=\left(33\:\frac{m}{s}\right)\left(\frac{1\:km}{1000\:m}\right)\left(\frac{3600\:s}{1\:hr}\right)=118.8\:km/hr$

### Part b

At 118.8 km/h, the car is traveling faster than the speed limit.

## Solution:

### Part a

$\displaystyle 100\:km/hr=\left(100\:\frac{km}{hr}\right)\left(\frac{1000\:m}{1\:km}\right)\left(\frac{1\:hour}{3600\:s}\right)=27.77\:m/s$

### Part b

$\displaystyle 100\:km/hr=\left(100\:\frac{km}{hr}\right)\left(\frac{1\:mile}{1.609\:km}\right)=62\:mi/hr$