Subtract 3-digit Numbers without regrouping Let us understand how to subtract 3-digit numbers through an example. Example 2: Subtract 141 from 943. Solution: To subtract the given numbers, follow these steps: Steps Solved Solve these Step 1: Arrange the numbers HTO HTO according to their place values. 943 784 –1 4 1 –3 3 2 HTO HTO 496 Step 2: Subtract the digits in the 943 –2 6 2 ones place. Write the difference in – 1 4 1 the ones place. That is, 3 – 1 = 2. 2 HTO HTO 636 Step 3: Subtract the digits in the 943 –1 3 0 tens place. Write the difference in –1 4 1 the tens place. That is, 4 – 4 = 0. 02 Step 4: Subtract the digits in HTO HTO the hundreds place. Write the 943 846 difference in the hundreds place. –4 2 0 That is, 9 − 1= 8. –1 4 1 So, 943 – 141 = 802. 802 Properties of subtraction 1) Zero property: When we subtract 0 from a number, the difference is the number itself. For example, 12 – 0 = 12 Subtraction 47
2) Before numbers property: When we subtract 1 from a number, we get the number that is just before it. For example, 35 – 1 = 34 3) Subtracting a number from itself: When we subtract a number from itself, the difference is 0. For example, 35 – 35 = 0 Application We use the concept of subtraction to solve some real-life situations. Let us see a few examples. Example 3: A class of 390 students is divided in red and blue groups. Among them, 150 students are in the red group. How many students are in the blue group? Solution: Number of students in the class = 390 HTO Number of students in red group = 150 39 0 Number of students in blue group = 390 – 150 −15 0 So, there are 240 students in the blue group. 2 4 0 Example 4: There are 52 candies in a jar. Children ate up 37 of TO them. How many candies are left in the jar? S olution: Number of candies in a jar = 52 4 12 Number of candies eaten by children = 37 52 Number of candies left in the jar = 52 – 37 −3 7 So, there are 15 candies left in the jar. 15 Higher Order Thinking Skills (H.O.T.S.) Let us now learn to frame a story sum based on subtraction. Example 5: Given 163 −120 = 43, frame a story sum. 48
Solution: Two numbers and their difference are given. We can use a situation to frame the story sum. Step 1: Think of a situation. For example, Shyam takes some chocolates to school on his birthday. Since it is subtraction, these chocolates should be given away. Step 2: Write the story in your words. Shyam takes 163 chocolates to school on his birthday. He shares 120 chocolates among his classmates. How many chocolates are left with him? Concept 5.2: Subtract Two 1-digit Numbers Mentally Think David had ` 9 with him. He gave ` 4 to his sister. How much amount was left with David? Can you find out without using pen and paper? Recall To subtract numbers mentally, we need to remember the correct order of numbers. Also we need to practise backward counting of numbers in the correct order. Let us recall how to write numbers backwards from 20 to 1. 20 1 Subtraction 49
& Remembering and Understanding Let us understand how to subtract two 1-digit numbers mentally, through this example. Example 6: Subtract mentally: 2 from 5 Solution: To subtract the given numbers mentally, follow these steps: Steps Solved Solve this 2 from 5 4 from 9 Step 1: Keep the bigger The bigger number is The bigger number is number in mind. If the two 5. So, keep 5 in mind. _____. So, keep _______ given numbers are the same, in mind. the answer is zero. Step 2: Keep as many fingers The smaller number is The smaller number is open as the smaller number. 2. So, keep 2 fingers _____. So, keep _______ open. fingers open. Step 3: Begin counting The number before The number before ___ backwards from the bigger 5 is 4. Count 2 fingers is ___. Count ___ fingers number. Fold as many fingers backwards as 4 backwards as ___, ___, as the smaller number. and 3. ___, and ____. Step 4: Write the number The difference of 5 The difference of 9 and obtained in step 3 as the and 2 is 5 – 2 = 3. 4 is 9 – 4 = ___. difference of the given numbers. Application We have seen how easy it is to subtract 1-digit numbers mentally. It is important to use mental subtraction of numbers in some real-life situations. Let us see a few examples. Example 7: Meena has 7 chocolates with her. She gave 3 of them to her sister. How many chocolates are left with Meena? Solution: Number of chocolates Meena has = 7 Number of chocolates Meena gave to her sister = 3 50
The bigger number is 7. The smaller number is 3. So, we keep the bigger number in the mind. We keep the smaller number on the fingers. That is, 7 in the mind, 3 on the fingers. But when we subtract we count backwards. Before 7, we count 3 fingers backwards as 6, 5 and 4. So, 4 chocolates are left with Meena. Example 8: Sameer is on an 8-day long vacation to Shimla with his family. He has spent 5 days there. How many days are left in his vacation? Solution: Number of days of vacation = 8 Number of days of the vacation spent = 5 The bigger number is 8 and the smaller number is 5. So, we keep the bigger number (8) in the mind. Keep the smaller number (5) on the fingers. But when we subtract, we count backwards. Before 8, we count 5 fingers as 7, 6, 5, 4 and 3. So, 3 days of Sameer’s vacation are left. Higher Order Thinking Skills (H.O.T.S.) Let us now see an example involving mental addition and subtraction together. Example 9: Priya had 6 pencils. She gave 2 pencils to her brother and 1 pencil to her sister. How many pencils did she give in all? How many pencils are left with Priya now? Solution: Total number of pencils with Priya = 6 Number of pencils she gave her brother = 2 Number of pencils she gave her sister = 1 We need to find the total number of pencils Priya gave away. So, add the number of pencils she gave to her brother and to her sister. Subtraction 51
The bigger number is 2 and the smaller number is 1. So, keep 2 in mind and 1 on the fingers. After 2, count 1 finger ahead. So, Priya gave away 3 pencils. Now, we need to find the number of pencils left. So, for this, subtract the number of pencils given away from the total pencils. The bigger number is 6 and the smaller number is 3. So, keep 6 in mind and 3 on fingers. Counting 3 fingers backwards from 6 we get 3. So, 3 pencils are left with Priya. Drill Time Concept 5.1: Subtract 2-digit and 3-digit Numbers 1) Subtract 2-digit numbers with regrouping. a) 25 – 18 b) 37 – 29 c) 48 – 19 d) 56 – 27 e) 90 – 25 2) Subtract 3-digit numbers without regrouping. a) 356 – 256 b) 197 – 106 c) 786 – 122 d) 476 – 111 e) 854 – 221 3) Word problems a) V ivaan has 33 cups in a box. He removed 17 of them and placed on the table. How many cups are left in the box? b) Baiju has 142 marbles with him in a basket. Out of these, he removed 100. How many marbles are left in the basket? Concept 5.2: Subtract Two 1-digit Numbers Mentally 4) Subtract the following mentally: a) 3 from 9 b) 2 from 7 c) 2 from 4 d) 7 from 8 e) 1 from 2 5) Word problems a) Sana drew 8 balloons out of which she coloured 6 red and the rest blue. How many balloons were coloured blue? b) R ohan made a bunch of 5 flowers out of which 1 flower fell down from his hand. How many flowers are left in his hand? 52
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