A particular star is at a distance of about 8.1 × 10¹³ km from the Earth. Assuring that light travels at 3 × 10⁸ m per second, find how long does light takes from that star to reach the Earth.

Mass of Mars is 6.42 × 10²⁹ kg and mass of the Sun is 1.99 × 10³⁰ kg. What is the total mass?

The distance between the Sun and the Earth is 1.496 × 10¹¹ km and distance between the Earth and the Moon is 3.84 × 10⁸ m. During solar eclipse the Moon comes in between the Earth and the Sun. What is distance between the Moon and the Sun at that particular time? (Question given is wrong, corrected.)

By what number should (–15)^–1 be divided so that the quotient maybe equal to (–5)^–1?

By what number should (–8)^–3 be multiplied so that that the product may be equal to (–6)^–3?