In this activity, we will be multiplying decimal numbers by whole numbers.

Don't worry - we have some steps to follow!

- The **first step** is to adjust the question so that there are no decimal numbers. Hooray!!

- The **second step** is to carry out the multiplication of the whole numbers.

- In the** third step**, we adjust the answer back to how it should be with decimals.

**Example 1**

Multiply

7.8 × 7

**Answer**

**Step 1:**

Adjust 7.8 so it becomes a whole number.

We do this by multiplying it by 10 to get rid of the decimal place.

7.8 × 10 = 78

This will mean that our answer will now be 10 times too big. But that is fine!

**Step 2:**

Now we work out 78 × 7

**Step 3:**

Now, remember that this is 10 times too big.

So we divide 546 ÷ 10 = 54.6

7.8 × 7 = **54.6**

The important thing is that our answer should have the same number of decimal places as our original decimal number - this means the same number of digits after the decimal point.

In our example, 7.8 has** one decimal place**, so our answer must also have one decimal place 54.6, which it does!

**Example 2**

Multiply

3.68 × 5

**Answer**

**Step 1:**

Adjust 3.68 so it becomes a whole number.

We do this by multiplying it by 100 to get rid of the 2 decimal places.

3.68 × 100 = 368

This will mean that our answer will now be 100 times too big. But that is fine!

**Step 2:**

Now we work out 368 × 5

**Step 3:**

Now, remember that this is 100 times too big.

So we divide 1840 ÷ 100 = 18.40 or we could write this as 18.4

3.68 × 5 = **18.4**

Does that make sense?

Let's have a go at some questions now.