what is the trade first method,i know the counting up method but don't what they mean by the trade first method
The "trade first" method, also known as the regrouping or borrowing method, is a technique used in arithmetic to subtract numbers with multiple digits. It is an alternative to the "counting up" or "counting on" method of subtraction.
The trade first method is based on the concept of borrowing or regrouping. When subtracting numbers, if the digit in the top number is smaller than the digit in the corresponding place value of the bottom number, we need to "trade" or "borrow" from the digit to its left. This allows us to subtract the larger digit from the smaller one.
Here is a step-by-step explanation of the trade first method:
1. Write down the two numbers you want to subtract, with the larger number on top and the smaller number below it.
2. Start from the rightmost digit (ones place) and compare the digits in the corresponding place value of the two numbers. If the digit in the top number is smaller, proceed to step 3. If it is larger or equal, move to the next digit to the left.
3. Borrow or regroup from the digit on the left by subtracting 1 from it. This increases the top number's digit by 10, allowing you to subtract the larger digit from the smaller one.
4. Cross out the borrowed digit in the top number and decrease the digit to its left by 1.
5. Subtract the smaller digit from the larger digit and write the result below the line. This becomes the new digit for that place value.
6. Move to the next digit to the left and repeat steps 2-5 until you have subtracted all the digits.
7. If there are any remaining digits in the top number, simply copy them down below the line.
8. The resulting numbers below the line represent the subtraction of the two given numbers.
The trade first method can be helpful when subtracting larger numbers, as it allows for a systematic and organized approach. Practice is key to becoming proficient in this method, as it requires understanding place value and borrowing.