A kingdom has fat monsters with 3 heads and 6 arms, and thin monsters with 1 head and 10 arms. A warrior counts 10 monsters with 16 heads. How many arms are there in total?
Identical polygonal paper pieces shaped like lizards are fitted together as shown. Each lizard must have one colour and neighbouring lizards must have different colours. What is the least number of colours needed?
In a class,3/5 of the girls and 1/2 of the boys wear glasses. Equal numbers of girls and boys wear glasses. Find the fraction of the class not wearing glasses.