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Division - Division as Repeated Subtraction

Grade 3ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Division is the method of distributing a group of items into equal parts. Imagine you have a basket of 1212 apples and you want to give an equal number to 33 friends; division helps you find out that each friend gets 44 apples.

Division as Repeated Subtraction is a way to find the answer by subtracting the same number over and over again until you reach zero. If you have 2020 and you keep subtracting 55, you are performing the division 20÷520 \div 5.

On a number line, repeated subtraction is visualized as jumping backward from a starting number. To solve 15÷315 \div 3, you start at 1515 and make equal jumps of 33 backward (1512963015 \rightarrow 12 \rightarrow 9 \rightarrow 6 \rightarrow 3 \rightarrow 0). The total number of jumps you take is the quotient.

The number you are dividing is called the Dividend. The number you are dividing by (or subtracting repeatedly) is called the Divisor. The final answer, which tells you how many times the divisor was subtracted, is called the Quotient.

The symbol for division is ÷\div. In a math sentence like 18÷6=318 \div 6 = 3, 1818 is the dividend, 66 is the divisor, and 33 is the quotient.

Division is the inverse (opposite) of multiplication. If 4×2=84 \times 2 = 8, then 8÷2=48 \div 2 = 4. You can visualize this as building a tower of blocks (multiplication) versus taking the tower apart block by block (division).

When you divide any number by 11, the quotient is always the number itself (e.g., 7÷1=77 \div 1 = 7). When you divide a number by itself, the quotient is always 11 (e.g., 9÷9=19 \div 9 = 1).

📐Formulae

Dividend÷Divisor=Quotient\text{Dividend} \div \text{Divisor} = \text{Quotient}

Total Quantity(Number in each group×Number of groups)=0\text{Total Quantity} - (\text{Number in each group} \times \text{Number of groups}) = 0

Divisor×Quotient=Dividend\text{Divisor} \times \text{Quotient} = \text{Dividend}

💡Examples

Problem 1:

Use repeated subtraction to find 12÷412 \div 4.

Solution:

Step 1: Subtract 44 from 1212. \n 124=812 - 4 = 8 (1st time) \n Step 2: Subtract 44 from 88. \n 84=48 - 4 = 4 (2nd time) \n Step 3: Subtract 44 from 44. \n 44=04 - 4 = 0 (3rd time) \n We subtracted 44 three times to reach 00. Therefore, 12÷4=312 \div 4 = 3.

Explanation:

To solve this using repeated subtraction, we start with the dividend (1212) and keep taking away the divisor (44) until we hit zero. The total count of subtractions performed is our answer.

Problem 2:

Solve 10÷210 \div 2 using the repeated subtraction method.

Solution:

  1. 102=810 - 2 = 8 \n 2. 82=68 - 2 = 6 \n 3. 62=46 - 2 = 4 \n 4. 42=24 - 2 = 2 \n 5. 22=02 - 2 = 0 \n We performed 55 subtractions.

Explanation:

By repeatedly taking away 22 from 1010, we see that it takes exactly 55 steps to reduce the number to zero. This means 1010 contains 22 exactly five times.