math
posted by ruby .
1. Which of the following expressions is written in scientific notation?
1. 73.4 x 105
2. 0.09 × 107
3. 80 x 103
4. 4.22 x 10–3
2. Which of the following is 0.0000000708 written in scientific notation?
1. 7.08 x 10–8
2. 7.8 x 10–8
3. 708 x 10–10
4. 70.08 x 10–9
3. Which expression represents the largest number?
1. 40.1 x 10–6
2. 4.1 x 10–7
3. 0.411 x 10–7
4. 0.04001 x 10–5
4. Which expression is equal to 1/8000 written in scientific notation?
1. 8.0 x 103
2. 1.25 x 10–4
3. 125 x 10–5
4. 1.25 x 104

A number written in scientific notation has to be between 1 and 10. The 10 to whatever power tells you whether to move the decimal point right or left depending on whether it is positive or negative. So for number one, the answer has to be 4. The actual number is 0.0042 because the decimal moves 3 places to the left since it is a 3.