Understanding the "Near a Base" Method
The "near a base" method is a useful mental math strategy that simplifies subtraction by rounding numbers to the nearest base, making calculations easier. Here’s how to apply this method to find 47 - 19.
Step 1: Identify the Base
- In this case, the nearest base for 19 is 20.
- Rounding 19 up to 20 will simplify the subtraction.
Step 2: Adjust the Numbers
- When we subtract 20 instead of 19, we need to adjust our result by adding back the difference.
- The calculation becomes:
- 47 - 20 = 27
Step 3: Correct the Adjustment
- Since we subtracted 20 instead of 19, we need to add back the 1 we took away (20 - 19 = 1).
- So, we add 1 to the result from the previous step:
- 27 + 1 = 28
Final Calculation
- Therefore, 47 - 19 equals 28.
Conclusion
- The correct answer to the problem 47 - 19 is indeed option 'A': 28.
- This method not only makes the calculation easier but also helps in developing number sense.
Using the "near a base" method is an efficient way to perform subtraction mentally, especially with numbers that are close to a round base.