Estimating long lengths

In your book, Maths Mela (Chapter 6), you guess long lengths by using lengths you already know. The book shows a blue whale, the biggest animal on Earth, about 30 metres long. Under the whale are 2 buses, end to end, and together they are as long as the whale.

So how long is one bus? 2 buses make 30 m, and 15 + 15 = 30, so one bus is about 15 m long. How many buses would be as long as two blue whales? Each whale is as long as 2 buses, so two whales are as long as 2 + 2 = 4 buses.

The book also shows a crocodile about 6 metres long. How many crocodiles make one whale? Count in sixes: 6, 12, 18, 24, 30. That is 5 crocodiles. An ostrich is about 3 m tall. If two ostriches stood one above the other, they would be 3 + 3 = 6 m tall, as long as the crocodile. The giraffe in the book stands in a tub 4 m high.

Using a length you know to guess a new length is called estimating. You also estimate in the long jump: first guess if a jump is less than 1 m, about 1 m or more than 1 m, then measure it.