A meter is 100 cm. A ball of string has 10m of string, and you multiply 10m by 100cm, you get 1,000cm. Then you multiply 40cm by 2, and you get 80cm, or two lengths of string. Then you multiply 35, which is half of 70, by 80, and that is 2,800 cm.2,800÷40cm=70And 100cm=1m.The teacher will therefore need 28 balls of string.
