You do by subtracting one from the previous number and adding 10 to the top number of the digits you are regrouping. Subtract those two digits and you should get your answer.
The simplest way is to line up the numbers so that their decimal points are aligned, and corresponding digits are also aligned according to their place value.
The simplest way is to line up the numbers so that their decimal points are aligned, and corresponding digits are also aligned according to their place value.
by adding or subtracting the values of the digits in the front place
same number of significant digits
as many as needed to satisfy the accuracy needed.
Because when adding or subtracting, the operations must take account of the place values of individual digits in the numbers. When multiplying, only the overall order of magnitudes are relevant for placing the decimal point in the product.
The least number of significant figures in any number of the problem determines the number of significant figures in the answer.
64
"Regrouping" is a more modern word for "borrowing". When subtracting with decimals, if you are trying to subtract a larger digit from a smaller digit, you "regroup" the next digit to the left by taking one away from it and adding 10 to the number you are subtracting from. Example 84 - 19 _____ You can't subtract 9 from 4, so you take one away from the next digit over (the 8) and add 10 to the 4. 14 - 9 is 5 in the ones digits 7 - 1 is 6 in the tens digits Now if you are subtracting mixed numbers, the regrouping process is essentially the same, except that instead of always regrouping by tens, we regroup by the denominator size. 8 1/5 - 3 3/5 ______ We can't subtract 3/5 from 1/5, so we regroup one unit from the 8 into 5 fifths. 7 6/5 -3 3/5 _______ 4 3/5 It is very easy when you get some practice doing it.
Alberto
Adding numbers using only the significant digits can introduce inaccuracies, for example if you are adding pi ten times using 4 decimal places of pi the answer is 31.416 but the right answer is 31.4159 . . Subtracting can give quite bad errors especially when two nearly equal numbers are subtracted. So for subtraction it's best to use more significant figures and round the answer to the required number of digits afterwards.