Final answer:
The signal time of 0.0078 seconds from a satellite to Earth written in scientific notation is 7.8 x 10^-3. The standard notation for Africa's surface area, assuming it is 1.17107 x 10^6 square miles, is 11,710,700 square miles.
Step-by-step explanation:
To write the number 0.0078 in scientific notation, we need to express it as a number between 1 and 10 multiplied by a power of 10. We can do this by moving the decimal point three places to the right, which gives us 7.8. Because we moved the decimal point to the right, we use a negative exponent to indicate how many places the decimal moved. Thus, 0.0078 becomes 7.8 × 10^-3 in scientific notation.
For the total surface area of Africa, the number given is ×1.17107 square miles, which seems to be incorrectly typed. Assuming it should be 1.17107×6 square miles, we can rewrite this in standard notation by understanding that the exponent indicates how many times to multiply 10 by itself. In this case, 1.17107×6 means we multiply 1.17107 by 1,000,000 (since 106 is 1,000,000), which gives us a standard notation of 11,710,700 square miles.