Physics - Electricity - Circuits - Kirchhoff's laws - What Goes In Must Come Out

Present a water pipe junction where one pipe (5 L/s) splits into three pipes. Ask: 'If pipe B carries 2 L/s and pipe C carries 1 L/s, what does pipe D carry?' (2 L/s - what goes in must come out!). This is Kirchhoff's Current Law! Then present a hiker walking in a loop on a hill. They start and end