Final answer:
The number 343,642 can be written in scientific notation as 3.43642 x 10^5.
Step-by-step explanation:
The number 343,642 can be written in scientific notation as 3.43642 x 10^5. To convert a number to scientific notation, we move the decimal place so that there is only one nonzero digit to the left of the decimal point, and multiply this number by a power of 10. In this case, we move the decimal point 5 places to the left to get 3.43642, and the power of 10 is 5, since we moved the decimal point 5 places to the left. So the correct answer is a) 3.43642 x 10^5.