Sunita travelled 15 km 268 m by bus, 7 km 7 m by car and 500 m on foot in order to reach her school. How far is her school from her residence?

Distance travelled by bus = 15 km 268 m

= 15 km + $\dfrac{268}{1000}$ km = 15 km + 0.268 km = 15.268 km

Distance travelled by car = 7 km 7 m

= 7 km + $\dfrac{7}{1000}$ km = 7 km + 0.007 km = 7.007 km

Distance travelled on foot = 500 m

= $\dfrac{500}{1000}$ km = 0.500 km

Total distance = 15.268 + 7.007 + 0.500

Writing in column form and adding:

$\begin{array}{r} \phantom{+}15.268 \ 7.007 \ +\space 0.500 \ \hline 22.775 \end{array}$

Hence, Sunita's school is 22.775 km or 22 km 775 m from her residence.