Verifying the Direction of the Decimal Shift
Verifying the direction of the decimal shift is a Grade 5 math skill in enVision Mathematics, Chapter 4: Use Models and Strategies to Multiply Decimals. Students check that when multiplying by a number greater than 1 (like a power of 10), the decimal moves right (value increases), and when multiplying by a number less than 1, the decimal moves left (value decreases). This verification step prevents common decimal direction errors.
Key Concepts
When multiplying a positive number by a power of 10 (a value greater than 1), the product must be greater than the original number. Moving the decimal point to the right increases the value of the number, while moving it to the left decreases the value.
Check: Is $Original \ Number \times Power \ of \ 10 Original \ Number$?
Common Questions
Which direction does the decimal move when you multiply by a number greater than 1?
The decimal moves to the right, increasing the value of the number. For example, 3.5 × 10 = 35.0 moves the decimal one place right.
Which direction does the decimal move when you multiply by a number less than 1?
The decimal moves to the left, decreasing the value. For example, 3.5 × 0.1 = 0.35 moves the decimal one place left.
How do you verify you shifted the decimal the right way?
Check the size of the product: if you multiplied by something greater than 1, your answer should be larger than the original number. If multiplied by less than 1, the answer should be smaller.
Where is verifying decimal shifts taught in enVision Grade 5?
Chapter 4: Use Models and Strategies to Multiply Decimals in enVision Mathematics, Grade 5.
Why is it important to check the direction of a decimal shift?
Moving the decimal the wrong way changes the answer by a factor of 10 or more. Verifying direction is a quick check that catches major errors before finalizing answers.