Answer:
-16
Explanation:
You want the difference (5.42x10^-15)-(4.98x10^-15).
Powers of 10
Consider the difference of the coefficients:
0.44
Multiplying and dividing by 10 gives ...
0.44 = 4.4/10 = 4.4 × 10^-1
When this is multiplied by the original numbers' factor 10^-15, we have ...
0.44 × 10^-15
= (4.4 × 10^-1) × 10^-15
Exponents are combined in the usual way:
= 4.4 × 10^-16
The value of k in 4.4×10^k is -16.
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Additional comments
The rule of exponents is ...
(a^b)(a^c) = a^(b+c)
The power of 10 multiplier of the number tells you the place value of the digit immediately to the left of the decimal point. Place values to the right of that have a power of 10 that is 1 less for each digit position. Perhaps the second attachment can help you visualize this.