Bài 15: Multiplication by carrying over

Yes Starry, you guessed right! This is another lesson and multiplication.

But you will learn something new and I’m sure you will find it interesting.

Before I go any further let me see if you remember what the multiplicative and the multiplier are.

Oh! Do you remember Starry?

The number to be multiplied is called the multiplicand and the number by which we multiply is called the multiplier.

Today, I will teach you multiplication by carrying over.

Now, what do we mean by caring over?

Let me explain, support we have to multiply a two digits number 23 by 4.

We begin by arranging the multiplication vertically.

Next we multiply the unit digit 3 in 23 by 4.

The product is 12.

The number 12 has 2 in the unit places and 1 in the ten places.

Write the 2 of 12 in the unit places of the product.

Starry, I know you are wondering what to do with the one ten of the number 12,

you carry over the 1 ten from 12 to the ten column and write the 1 ten above the ten in the multiplicand.

That is about 2.

Now multiply the ten digit 2 in 23 by 4, we get 8 tens.

Add this we carrying over 1, we get 9 tens, write in the product in the ten places. The product is 92.

Wasn’t that easy?

Starry, help me multiply 19 by 4.

We first multiply the unit digit 9 in 19 by 4. The product is 36.

Write the 6 of 36 in the unit places of the product,

carry over the 3 tens from 36 to the ten column and write the 3 above 1.

Now multiply ten digit 1 in 19 by 4, we get 4 tens.

Add this we carry over 3, we get 7 tens.

Write digit in the ten places in the product. The product is 76.

Now Starry, here the multiplication slightly different.

Support we have to multiply 43 by 5.

Multiply the unit digit 3 in 43 by 5. The product is 15.

Write the 5 of 15 in the unit place of the product.

Carry over the 1 ten from 15 to the ten column and write the 1 above 4.

Now multiply the 4 tens in the multiplicand by 4. The product is 20 tens.

Add this we carry over ten, 20 tens plus 1 ten equal 21 tens.

Write 1 in the ten places in the product and meet a new place to write the 2 hundreds. The product is 215.

Come Starry, let me see if you have understood, let us do the next one together.

Multiply 85 by 9.

Multiply the unit digit 5 in 85 by 9. The product is 45.

Write the 5 of 45 in the unit places of the product.

Carry over the 4 tens from 45 to the ten column and write the 4 above 8.

Now multiply the 8 tens in the multiplicand by 9, the product is 72 tens.

Add this we carry over 4 tens, 72 tens plus 4 tens equal 76 tens.

Write 6 in the ten places and 7 in the hundred places in the product. The product is 765.

And now we will provide what we have learnt.

Multiply 29 by 2.

We first multiply the unit digit 9 in 29 by 2, the product is 18.

Write the 8 of 18 in the unit places of the product,

carry over 1 ten from 18 to the ten column and write it above 2.

Now multiply the ten digit 2 in 29 by 2, we get 4 tens.

Add this we carry over 1 ten, we get 5 tens, write it in the ten places in the product. The product is 58.

Multiply 18 by 5.

First multiply the unit digit 8 in 18 by 5, the product is 40.

Write the 0 of 40 in the unit places of the product.

Carry over the 4 tens from 40 to the ten column and write it above 1.

Now multiply the ten digit 1 in 18 by 5, we get 5 tens.

Add this we carry over 4 tens, we get 9 tens, write it in the ten places in the product. The product is 90.

Finally, let multiply 70 by 4.

Multiply the unit digit 0 in 70 by 4, the product is 0.

Write the 0 in the unit places of the product.

Next, multiply the 7 tens in the multiplicand by 4, the product is 28 tens.

Write 8 in the ten places, and 2 in the hundred places in the product. The product is 280.

Starry, you have now learnt how to carry over to the ten places while multiply two digit numbers