Question

an astronomical unit (au) is equal to the average distance from the sun to earth. answer parts a and b.
a. an astronomical unit is about 92,955,807 miles. use a single digit times a power of ten to estimate this value to the nearest ten million miles.
9 · 10^7 miles
(type whole numbers.)
b. venus is about 7.2 · 10^(-1) au from the sun. mars is about 1.5 au from the sun. which planet is closest to earth?
o mars
o venus

Explanation:

Step1: Round to nearest ten - million

The number 92,955,807 is closer to 90,000,000 than 100,000,000. 90,000,000 can be written as $9\times10^{7}$.

Step2: Calculate distances from Earth

Earth is 1 AU from the Sun. The distance between Earth and Venus is $|1 - 0.72|= 0.28$ AU. The distance between Earth and Mars is $|1.5 - 1| = 0.5$ AU. Since $0.28<0.5$, Venus is closer to Earth.

Answer:

a. $9\times10^{7}$
b. Venus