The answer is: " 6.8 * 10¹⁰ " .
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Note: 68 billion = 68,000,000,000 ;
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6.8 * 10^(raised to the number of digits that following the
{"single, whole number digit"—which is: "6" } ;
⇒ (which comprises the number "8" PLUS the number of zeros that follow).
So, we have the number: "8" ; which is: 1 digit ;
and we have: nine "0's" ; which are: 9 digits;
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⇒ for a total of: "1 digit PLUS 9 digits = 10 digits" .
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So; 68 billion = 6.8 * 10^10 ; that is;
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⇒ " 6.8 * 10¹⁰ " .
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