* Multiplying a three-digit number by a one-digit number : (Textbook page 75)
919
TTH
1
4
2
Х
7
7
2
Oral Work
Understand the solved example on multiplication : 427 x 7
Arrange vertically and multiply.
First, multiply 7 units by 7 units.
Th H
The product is 49 units. 49 units = 4 tens +9 unit
Write 9 in the units place.
Write 4 T in the carried over tens place.
29 18 9
Now, 2 T 7= 14 T. Add 4 T carried over. The sum is 18 T.
18 T=1H +8 T. Write 8 in the tens place. Write 1 H in the carried
over hundreds.
4 H x 7 = 28 H. Add 1 H carried over. The sum is 29 H. 29 H=2 Th +9 H.
Write 9 in the hundreds place and put 2 in the thousands place.
We have to make a thousands place to write this multiplication.
Now, the digits in the Th, H, T, U places are 2, 9, 8, 9. The answer is 2989.
Therefore, 427 x 7 = 2989.
ber by
two-digit number : (Textbook page 76)
Answers
Answer:
Multiplication
When writing, the common sign for multiplication is ‘×’. In spreadsheets and some other computer applications the ‘*’ symbol (or asterisk) is used to indicate a multiplication operation.
In order to perform multiplication calculations without a calculator or spreadsheet you will need to know how to add numbers. See our Addition page for help with adding.
When you ‘multiply’ or ‘times’ a number you add it to itself a number of times, for example 4 multiplied by 3 is the same as saying 4 + 4 + 4 = 12. Multiplication is therefore a quicker way of adding the same number many times, for example 3 × 4 = 12. This calculation is the same as saying, if I have 3 bags of 4 apples, how many apples do I have in total?
Basic Rules of Multiplication:
Any number multiplied by 0 is 0. 200 × 0 = 0
Any number multiplied by 1 stays the same. 200 × 1 = 200.
When a number is multiplied by two we are doubling the number. 200 × 2 = 400.
When a whole number is multiplied by 10 we can simply write a 0 at the end (there is one zero in 10 because it is 1 × 10). 200 × 10 = 2000.
When multiplying by 100 we write two zeros at the end, by a thousand we write three zeros at the end and so on. 4 × 2000 for example is 4 × 2 = 8 with 3 zeros: 8000.
For simple and quick multiplication it is useful to memorise the multiplication or 'times table’ as shown below. This table gives the answers to all multiplications up to 10 × 10. To obtain the answer to 4 × 6, for example, find 4 on the top (red shaded) line and find 6 on the left hand (red shaded) column – the point where the two lines intersect is the answer: 24.
It doesn't matter which way around you search for the numbers; if you find 4 in the first column and 6 in the first row you get the same answer, 24.
Multiplication Table
× 1 2 3 4 5 6 7 8 9 10
1 1 2 3 4 5 6 7 8 9 10
2 2 4 6 8 10 12 14 16 18 20
3 3 6 9 12 15 18 21 24 27 30
4 4 8 12 16 20 24 28 32 36 40
5 5 10 15 20 25 30 35 40 45 50
6 6 12 18 24 30 36 42 48 54 60
7 7 14 21 28 35 42 49 56 63 70
8 8 16 24 32 40 48 56 64 72 80
9 9 18 27 36 45 54 63 72 81 90
10 10 20 30 40 50 60 70 80 90 100
The table above can help us quickly calculate the answer to the following problem. Megan is taking her three brothers to the cinema, she needs to buy 4 tickets in total and each ticket costs £8. How much will the total cost of the trip be? We need to calculate 4 lots of £8, which is written 4 × 8.
Find 4 on the vertical red column and 8 on the horizontal red column, the answer is in the cell where the two lines intersect: 32. The cost of the trip to the cinema will therefore be £
Answer:
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Explanation: