Metro maps

In your book, Maths Mela (Chapter 14, Maps and Locations), the children get off the bus at the Qutb Minar metro station. To reach the zoo they must get off the metro at the Supreme Court station. The book gives a map of the Delhi Metro.

Every map has a key, a small box that tells what each symbol means. On the metro map, each coloured line is one metro route: the Red Line, Yellow Line, Blue Line, Magenta Line and others. A small circle on a line is a station. A special mark shows an interchange station: a station where two lines meet, so you can get off one line and change to the other.

Qutb Minar is on the Yellow Line, and Supreme Court is on the Blue Line. So the children must change lines at least once. One way: ride the Yellow Line to Rajiv Chowk, which is an interchange station of the Yellow and Blue Lines, change there, and ride the Blue Line to Supreme Court.

Lali has another plan: take the Yellow Line and change at Hauz Khas to the Magenta Line. But the Magenta Line does not reach Supreme Court. It meets the Blue Line at Botanical Garden, so the children must change a second time there, onto the Blue Line. To find the route that passes the fewest stations, count the stations along each route and compare the counts.