What are the rules in subtractin in significant notation?

Answer 1

First ensure that the exponents (the powers of the multipliers of the tens) are the same - if necessary adjust the smaller number by shifting the decimal point left until the powers are the same; for example if the exponents are ``x 105'' and ``x 103'' shift the decimal point of the second number 5 - 3 = 2 places to the left and then the numbers will have the same exponents.

Now, align the decimal points and subtract the mantissae (the numbers before the ``x 10'' s) as usual.

Finally, adjust the result to correct into standard form if necessary by shifting the decimal point.

Examples:

2.3 x 107 - 2.275 x 106 = 2.3 x 107 - 0.2275 x 107

= (2.3 - 0.2275) x 107

= 2.0725 x 107

2.3 x 107 - 2.275 x 107 = (2.3 - 2.275) x 107

= 0.025 x 107

= 2.5 x 105