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What is Checking an Answer (Maths Skill)?
Grade Level:
Pre-School – Class 2
All domains without exception
Definition
What is it?
Checking an answer is a maths skill where you review your calculation to make sure it is correct. It means going back over your steps or using a different method to confirm your final result. This helps you catch any mistakes before they become a problem.
Simple Example
Quick Example
Imagine you just added up your pocket money for the week: Rs. 20 (Monday) + Rs. 30 (Wednesday) + Rs. 50 (Saturday) = Rs. 100. To check your answer, you might add them again, perhaps in a different order, like Rs. 50 + Rs. 30 + Rs. 20. If you get Rs. 100 again, your answer is likely correct!
Worked Example
Step-by-Step
PROBLEM: You bought 3 packets of biscuits for Rs. 15 each and a cold drink for Rs. 20. How much did you spend in total? You calculated Rs. 15 + Rs. 15 + Rs. 15 + Rs. 20 = Rs. 65.
---STEP 1: Identify the main calculation: Total spent = (cost of biscuits) + (cost of cold drink).
---STEP 2: Re-calculate the cost of biscuits using multiplication: 3 packets * Rs. 15/packet = Rs. 45.
---STEP 3: Add the cold drink cost to the biscuit cost: Rs. 45 + Rs. 20 = Rs. 65.
---STEP 4: Compare this new total with your original answer. Both are Rs. 65.
---ANSWER: The original answer of Rs. 65 is confirmed as correct.
Why It Matters
Checking your answers is super important because it builds confidence in your maths skills and helps you avoid errors in exams. This skill is vital for engineers designing bridges, accountants managing money, and even shopkeepers giving change, ensuring everything adds up perfectly.
Common Mistakes
MISTAKE: Only looking at the final answer and assuming it's right. | CORRECTION: Always re-do the calculation or use an inverse operation to verify your answer, even if it looks correct.
MISTAKE: Using the exact same method to check, which might repeat the original error. | CORRECTION: Try a different approach, like using addition to check subtraction, or multiplication to check division.
MISTAKE: Not checking calculations that seem 'too easy'. | CORRECTION: Every calculation, big or small, deserves a quick check. Even simple sums can have silly mistakes.
Practice Questions
Try It Yourself
QUESTION: You subtracted 25 from 70 and got 45. How can you check this answer using addition? | ANSWER: 45 + 25 should equal 70. Since 45 + 25 = 70, the answer is correct.
QUESTION: A train travels 120 km in 2 hours. You calculated its speed as 60 km/hour. How would you check this using multiplication? | ANSWER: If the speed is 60 km/hour, then in 2 hours it should travel 60 km/hour * 2 hours = 120 km. This matches the problem, so the answer is correct.
QUESTION: Your mom bought vegetables for Rs. 85 and fruits for Rs. 115. She paid with a Rs. 500 note and got Rs. 300 back. Is her change correct? Show how you'd check. | ANSWER: Total spent = Rs. 85 + Rs. 115 = Rs. 200. Change expected = Rs. 500 - Rs. 200 = Rs. 300. The change received (Rs. 300) matches the expected change, so it is correct.
MCQ
Quick Quiz
Which of these is the BEST way to check the answer to 100 - 35 = 65?
Ask a friend if their answer is also 65.
Do the subtraction 100 - 35 again.
Add 65 and 35 to see if it equals 100.
Guess if 65 seems like a reasonable answer.
The Correct Answer Is:
C
Adding the answer (65) to the number subtracted (35) is an inverse operation that correctly verifies the original subtraction. Re-doing the subtraction might lead to the same error, and guessing or asking a friend aren't reliable checks.
Real World Connection
In the Real World
When you use a calculator on your phone, like for splitting a bill at a restaurant, you might quickly add up the amounts again on paper or use a different calculator app to double-check. Similarly, cashiers at kirana stores often count change back to you in two ways to ensure they haven't made a mistake, which is a form of checking their answer.
Key Vocabulary
Key Terms
CHECKING: Reviewing something for accuracy | VERIFY: To confirm that something is true or correct | INVERSE OPERATION: An operation that undoes another operation (e.g., addition is inverse of subtraction) | ACCURACY: Being correct or precise
What's Next
What to Learn Next
Now that you understand checking answers, you can move on to 'Estimation'. Estimation helps you predict a rough answer before you calculate, which is another great way to see if your final, checked answer is reasonable. Keep practicing!
