How do i write 2.345 x 10^-4cm out of scientific notation?

In the reading, yao chen-yuan describes traveling to deliver a message. why was he willing to risk danger to travelto tientsin? he wanted to the boxers with their cause

If 1.63 times 10 negative 4 of helium dissolves in 100.0g of water, what is the concentration in parts per million

How did planetesmals form planets? a. they broke apart into smaller chunks.b. they collided and stuck together.c. they cooled and pulled ice together.d. they began to rotate.