Final answer:
The number 343,642 written in scientific notation is 3.43642 x 10^5, moving the decimal 5 places to the left.
Step-by-step explanation:
To write the number 343,642 in scientific notation, you first find the decimal place after the first non-zero digit. Since 343,642 is a large number, the decimal will move to the left. We move the decimal 5 places to the left to get 3.43642. This tells us our exponent for 10 will be 5 since the decimal moved 5 places. So, the scientific notation of 343,642 is 3.43642 x 10^5.