How do you determine reasonableness?
How do you determine reasonableness?
Subtract the smaller number from the larger one to check for reasonableness. In this example, you would subtract 600 from 651 to get 51. The numbers are reasonably close, so you can probably accept that 651 is the correct answer.
How do you estimate a multiplication problem?
To estimate, students round two and three-digit numbers before multiplying, but this rounding can be done in several different ways. Various exercises and word problems follow. To estimate the result of multiplication (product), round the numbers to some close numbers that you can easily multiply mentally.
Can you tell how many digits will be in the answer of a multiplication problem?
2 Answers. You can take log10 of each of the numbers being multipled, sum them, floor them, then add one to get the number of digits. i.e. In your last example of 2*12321*1000, which is actually equal to (you missed a 0, so it has 8 digits).
How do you estimate sums and differences of decimals?
Students learn to estimate the sum or difference of two decimals by first rounding each decimal to the nearest whole number, then adding or subtracting. For example, to estimate the sum of 4.94 and 2.185, round 4.94 up to 5, and round 2.185 down to 2, to get 5 + 2, which equals 7.
How do you find the difference between decimals?
Subtracting Decimals
- Write down the two numbers, one under the other, with the decimal points lined up.
- Add zeros so the numbers have the same length.
- Then subtract normally, remembering to put the decimal point in the answer.
How do you estimate when multiplying decimals?
Estimating When Multiplying Decimals Remember to look at the number in the tenths place. If the number is less than 5, round the number down to the nearest whole number. If the number is equal to or greater than 5, round the number up to the nearest whole number. First, round the decimal to the nearest whole number.