The number is already in decimal form so why would you want to estimate it in decimal form???
0.75 is a good estimate.
I would estimate the value of 0.87 to be around 0.86999999...
0.235 * 0.6891 = 0.1619385 What's to estimate? The total decimal places in the multiplicands is the total in the answer.
The range of a single number - with or without a decimal - is zero.
It depends on your level of numerical skill. You can convert the decimal to an approximate fraction and estimate the sum of the two fractions, or you can convert the fraction to an approximate decimal and estimate the sum of the two decimals or, if you are more able you just estimate their sum directly.
2.4*63
0.8
by estimating the number after the decimal
The answer depends on what the decimal is: the processes for 9999.02 and 0.02 are very different.
YOU CAN estimate it by if your product has more than 5
352.84/10