Learning Resources Simple Stopwatch. Timing practice even youngsters can master! This simple stopwatch features just three easytouse simple buttons (green for go, red for stop and yellow for clear) and an easyto read large digital display that shows minutes, seconds and hundredths of a second. This colourful simple stopwatch measures 7cm H. Requires one 1.5V buttoncell battery (included). Colours may vary. Suitable for ages 5+