# Column subtraction 5: Captivating Caribou

## Learning Objective

We are learning how to subtract whole numbers with more than 4 digits using the formal written method of column subtraction. **(with more than one exchange, including exchanges across more than one place value)**.

## Clip Description

Reindeer and caribou are the same animal. In Europe, they are called reindeer. In North Ameica, they are called caribou. These incredible animals feed, rest and travel in herds of ten to a few hundred. However, in spring, they often form super-herds of 50,000 to 500,000 animals in their search for food.

In this fascinating clip, we meet the Nenet people of Siberia as they begin a 500 mile journey across ice and snow. They are travelling with a huge herd of reindeer,who need to find new feeding grounds. No-one knows for certain whether it is the reindeer that lead the people or vice versa.

## Whiteboard Number Challenge

In the clip, the numbers 3 and 7 were mentioned. (The herd was 3 miles long. The herd had covered less than 7 miles.) These numbers are prime numbers.

**Can you calculate the sum total of the first 5 prime numbers?**

**Can you calculate the sum total of the first 10 prime numbers?**