30. What is 6.7times 10^4 written as an ordinary number? a. 6700 b. 670 oo c. 670000 d. 0.00067

To convert $6.7\times 10^{4}$ to an ordinary number, we need to move the decimal point 4 places to the right, since the exponent is positive.<br /><br />Starting with 6.7, we move the decimal point 4 places to the right, filling in with zeros as needed:<br /><br />6.7 → 67 → 670 → 6700 → 670000<br /><br />Therefore, $6.7\times 10^{4}$ written as an ordinary number is 670000.<br /><br />The correct answer is c. 670000.