Mr Mohammad took a taxi from home to his office.
His taxi fare was based on the charges shown below.

First 1 kilometre or less	$4.30
Every additional 400 m or less	$0.24
Every 45 seconds of waiting or less	$0.24

The taxi stopped once at a traffic light and travelled a total distance of 7 km to reach his office. Mr Mohammad paid $9.10. What was the longest possible duration the taxi stopped at the traffic light? Ans: ___

1. Calculate the remaining distance after the first kilometre

Remaining distance $= 7\text{ km} - 1\text{ km} = 6\text{ km} = 6000\text{ m}$

2. Calculate the cost of the remaining distance

Number of $400\text{ m}$ blocks $= \frac{6000}{400} = 15$
Cost for remaining distance $= 15 \times \char36{}0.24 = \char36{}3.60$

3. Calculate the amount paid for waiting time

Total cost for distance $= \char36{}4.30 + \char36{}3.60 = \char36{}7.90$
Amount paid for waiting $= \char36{}9.10 - \char36{}7.90 = \char36{}1.20$

4. Calculate the longest possible waiting duration

Number of $45$-second waiting blocks $= \frac{\char36{}1.20}{\char36{}0.24} = 5$
Since the charge is for every $45$ seconds or less, the longest possible duration for $5$ blocks is exactly $5 \times 45\text{ s}$.
Longest duration $= 5 \times 45 = 225\text{ seconds}$