In estimating- what is the counting-up method and the trade-first method?
counting up.
Example 432-195.
take five to make 200, then 200 more (total 205) to make 400, then add 32, total 237.
Trade-first method.
http://ouronlineschools.org/Schools/NC/Demoschool/3rdGrade/Math/Reviews/TradeFirstSubtractionMethod.htm
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LOSER!
In estimation, the counting-up method and the trade-first method are two different approaches used to quickly estimate a sum or difference. Here's an explanation of both methods:
1. Counting-up Method:
The counting-up method is used to estimate the sum of two numbers. Here's how it works:
- Start with the larger number.
- Count up from the larger number in ones to reach the other number.
- Keep a running count of each number you pass while counting up.
- The final count will give you an estimate of the sum.
For example, let's say you want to estimate the sum of 47 and 28 using the counting-up method:
- Start with 47.
- Count up: 48, 49, 50, 51...
- Stop when you reach 28.
- The final count is 23, so the estimate for the sum is 47 + 28 ≈ 75.
2. Trade-first Method:
The trade-first method is used to estimate the difference between two numbers. Here's how it works:
- Start with the larger number.
- Trade or subtract a convenient amount from both numbers.
- Find the difference between the new numbers.
- The resulting difference will give you an estimate of the original difference.
For example, let's say you want to estimate the difference between 87 and 61 using the trade-first method:
- Start with 87.
- Trade 3 from both numbers: 84 and 58.
- Find the difference between the new numbers: 84 - 58 = 26.
- The resulting difference is 26, so the estimate for the original difference is 87 - 61 ≈ 26.
Both methods are quick estimation techniques that can be useful when you need a rough estimate without performing precise calculations.