Page 79 - Touchpad Mathematics_Ver1.0_C4

example 2. Multiply 210 by 4.
Solution.
Step 1. Multiply the ones. Step 2. Multiply the tens. Step 3. Multiply the hundreds.

H T O H T O H T O

2 1 0 2 1 0 2 1 0

× 4 × 4 × 4

0 4 0 8 4 0

0 × 4 = 0 ones 1 × 4 = 4 tens 2 × 4 = 8 hundreds

So, 210 × 4 = 840.
Multiplication of a 2- and 3-digit Number by a 1-digit Number (With regrouping)

example 3. Multiply 25 by 3.
Solution.

Step 1. Multiply the ones and regroup. Step 2. Multiply the tens and add the
carried over tens.
T O T O

1 1

2 5 2 5
× 3 × 3

5 7 5

5 × 3 = 15 ones = 1 ten 5 ones 2 × 3 = 6 tens and 6 tens + 1 ten = 7 tens
So, 25 × 3 = 75.

example 4. Multiply 245 by 4.
Solution.
Step 1. Multiply the ones and regroup. Step 2. Multiply the tens, add the carried

over tens and regroup.

H T O H T O
2 1 2

2 4 5 2 4 5

× 4 × 4

0 8 0

5 × 4 = 20 ones = 2 tens 0 ones 4 × 4 = 16 tens
16 tens + 2 tens = 18 tens = 1 hundred 8 tens

77
Multiplication