Samacheer Kalvi Class 4 Maths Solutions Term 3 Chapter 2 Numbers Exercise 2.7

Tamilnadu Samacheer Kalvi 4th Maths Solutions Term 3 Chapter 2 Numbers Ex 2.7

Simplify the Following Multiplication Facts by Adding Partial Products.

Question 1. 9 × 42
Answer: First, we break down 42 into its parts: \( 42 = 40 + 2 \). Next, we multiply each part by 9. We find \( 40 \times 9 = 360 \) and \( 2 \times 9 = 18 \). Finally, we add these partial products together: \( 360 + 18 = 378 \). This method makes multiplying larger numbers easier.
In simple words: Break 42 into 40 and 2. Multiply both by 9 to get 360 and 18. Then add these two numbers to get the final answer.

🎯 Exam Tip: Always show the breaking down of the number and each partial product step clearly to get full marks.

Question 2. 3 × 78
Answer: We begin by splitting 78 into two easier numbers: \( 78 = 70 + 8 \). Then, we multiply each of these parts by 3. This gives us \( 70 \times 3 = 210 \) and \( 8 \times 3 = 24 \). Adding these results gives us the total: \( 210 + 24 = 234 \). This strategy is helpful for mental math.
In simple words: Split 78 into 70 and 8. Multiply each by 3 to get 210 and 24. Add these two results to find the answer.

🎯 Exam Tip: Remember to carry over any tens or hundreds correctly when adding your partial products if you are doing it in columnar form.

Question 3. 36 × 12
Answer: Let's break down 36 into its tens and units: \( 36 = 30 + 6 \). Next, we multiply each part by 12. We calculate \( 30 \times 12 = 360 \) and \( 6 \times 12 = 72 \). Adding these two values gives us the final product: \( 360 + 72 = 432 \). This method simplifies multiplication by using smaller, more manageable steps.
In simple words: Break 36 into 30 and 6. Multiply both by 12, which gives 360 and 72. Add these two numbers to get the total 432.

🎯 Exam Tip: When multiplying by a two-digit number, make sure to align your partial products correctly before adding them, especially if you write them out vertically.

Question 4. 18 × 19
Answer: We can simplify this by breaking 19 into \( 19 = 10 + 9 \). Now, we multiply 18 by each part of 19. So, \( 10 \times 18 = 180 \) and \( 18 \times 9 = 162 \). Finally, we add these partial products: \( 180 + 162 = 342 \). Breaking numbers down helps avoid large single multiplications.
In simple words: Split 19 into 10 and 9. Multiply 18 by 10 (get 180) and 18 by 9 (get 162). Add 180 and 162 to get 342.

🎯 Exam Tip: Practicing your multiplication tables up to 12 or 20 can significantly speed up the calculation of partial products like \( 18 \times 9 \).

Question 5. 68 × 31
Answer: To solve this, we break 68 into \( 68 = 60 + 8 \). Then, we multiply each of these parts by 31. This results in \( 60 \times 31 = 1860 \) and \( 8 \times 31 = 248 \). Adding these two partial products together gives us the final answer: \( 1860 + 248 = 2108 \). This method is good for multiplying two-digit numbers.
In simple words: Break 68 into 60 and 8. Multiply 60 by 31 to get 1860. Multiply 8 by 31 to get 248. Add 1860 and 248, which equals 2108.

🎯 Exam Tip: When multiplying by a number like 31, remember that \( 31 = 30 + 1 \). You can break down either number, but pick the one that makes mental calculation easiest.

Question 6. 42 × 21
Answer: We will break down 42 into its tens and units: \( 42 = 40 + 2 \). Now, we multiply each of these parts by 21. We calculate \( 40 \times 21 = 840 \) and \( 2 \times 21 = 42 \). Adding these partial products together gives us the final result: \( 840 + 42 = 882 \). This method makes complex multiplication simpler.
In simple words: Split 42 into 40 and 2. Multiply 40 by 21 to get 840. Multiply 2 by 21 to get 42. Add 840 and 42 together, which is 882.

🎯 Exam Tip: Always double-check your addition of the partial products, as a small error there will lead to an incorrect final answer.