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# Multiply by 1-Digit Numbers

Sep 20, 2022

## Key Concepts

• Array multiplication
• Use place value for multiplication

### Multiply by 1-digit numbers

What are 1–digit numbers?

The smallest one-digit number is 1 (one).

The greatest one-digit number is 9.

All the digits become numbers when used as a number.

Example 1: 2 digits by 1–digit multiplication.

Example 2: 2 digits by 1–digit multiplication.

Multiply 8 × 26.

Multiply the ones 8 × 6 = 48

Multiply the tens 8 × 20 = 160

Add the tens and ones.

### Array multiplication

Example 1:

A Ferris wheel completes a rotation for 38 seconds. How many seconds in all would it take to complete 4 rotations?

Solution:

One way to record multiplication.

152 seconds will take to 4 rotations.

Example 2:

A polar bear climbs on a rock every morning to eat a breakfast of 29 fish. How many fish in one week will the polar bear eat?

Solution:

Multiply 29 × 7.

Polar bear eats 203 fishes during the week.

### Use place value for multiplication

At Kelvin’s birthday party, all his 4 friends get a surprise goodie bag. 38 candies are in each bag. How many candies do his friends get in all?

Solution:

Another way to record multiplication

Step1:

Multiply by the ones.

Record the 2 ones.

Record the 3 tens.

Step 2:

Multiply by the tens.

His friends get 152 candies.

Example 2:

Charmin plays outside for 65 minutes in one day. How many minutes will she play in 8 days?

Solution:

She will get 520 minutes to play.

Example 3:

Tim bought 5 packs of balls. If each pack contains 134 balls, how many balls does Tim have in all?

Solution:

Multiply 134 × 5.

Step 1:

First multiply the ones.

Step 2:

Multiply the tens.

Step 3:

Multiply the hundreds

So, 134×5 = 670.

Tim has 670 balls.

## Exercise

• Find each product. Estimate to check if your answer is reasonable.

307

×   2

553

×   3

• Find the product.

25

× 3

_________

_________

1172

×    4

• Use place value to explain each step to find 4 × 3, 678.
• Use the partial product model to find the product of 9 × 38
• Fill the missing numbers.
• Through the place value of multiplication, find the product.
• Ria ordered 9 boxes of fruits. There are 32 fruits in each box. How many fruits did ria order?
• A flashlight requires 2 batteries to function. How many batteries in all would 7 such
flashlights require?
• Norah uses an ounce of butter to bake 9 cookies. How many cookies can she bake
with 18 ounces of butter?
• A tour operator owns a small fleet of 8 cars of the same make. Each car is filled with
2 liters of engine oil. How many liters in all have been filled in the cars?
• Vanessa sells 6 cakes every day. How many cakes will she sell in 20 days?

### What have we learned

• Understand 1 digit numbers.
• Understand how to multiply by 1 digit through array model.
• Understand how to multiply by 1 digit through place value.
• Adding partial products.
• Identify the place value.

### Concept Map

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