The answer: " 6.6 * 10 ⁴ " .
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Explanation:
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(5.3 * 10⁴) + (1.3 * 10⁴) = (5.3 + 1.3) * 10⁴ ;
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Note: "2a + 3a = (2+3) a = 5a " ;
In other words, we are combining the "like terms" ;
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(5.3 + 1.3) * 10⁴ = 6.6 * 10⁴ .
We retain the "2 (two) significant figures" ; because "5.3" and "1.3" both have 2 (two) significant figures.
The answer: " 6.6 * 10⁴ " ; is already written in scientific notation.
(Note: To write a number in scientific notation; one takes the nearest "non-zero, whole number" that appears to the nearest "left side of the number", writes down that "digit:. Then, if there are any numbers to the left or right or that number, one writes a "decimal point" after the aforementioned digit.
Then, one writes the "multiplication sign" (i.e, the [*] or [ˣ] symbol) ; then followed by the number; "10", raised to the appropriate exponent ("power").
If the aforementioned [single, aforementioned, non-zero, integer digit] has numbers ["digits"] to to the left, then the exponent {"power"] digit written IS that very [number of digits; i.e, number of decimal spaces] to the left [of that aforementioned, single, non-zero, integer digit] ; yet the actual "exponent" {"power"} digit is: "-4" ; since we are counting to the LEFT.
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Examples:
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" 0.0000404 " ; written in "scientific notation" ; is:
" 4.04 * 10⁻⁴ " . {Note: The "10 ⁻ ⁴ " ; the "FOUR" (in the "-4") comes from moving back "FOUR (4) decimal places".
Other example:
" -0.0003 "; written in scientific notation; is: " 3 * 10⁻⁴ ".
If the digits are to the "right" of the "whole number digit" that was written down; then the appropriate number is a positive number". NOTE: FOR THE APPROPRIATE "exponent" or "power"; if one is dealing with a decimal value, and the decimal value ends in a "zero" as given; or, as an obtained measurement; then we include the "zero" when converted that value to scientific notation.
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Example:
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70 ; written in scientific notation; is: "7 * 10¹ " .
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70.0 ; written in scientific notation; is: "7.00 * 10¹ "
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- 0.05 ; written in scientfic notation; is: " -5 * 10⁻² " .
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0.0600 ; written in scientific notation is: "6.0 * 10⁻² " .
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NOTE: I provide this explanation to show that our answer ;
6.6 * 10⁴ ; is already in scientific notation; and that the number of significant figures is correct; since both values in the original problem have exactly 2 (TWO) significant figures.
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