Question (i) - Page 42 - Getting a sense of Large Numbers - Chapter 2 Class 8 - Power Play (Ganita Prakash)

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Question (i) - Page 42 Calculate and write the answer using scientific notation: (i) If one star is counted every second, how long would it take to count all the stars in the universe? Answer in terms of the number of seconds using scientific notation.To find the time it would take, you need to know the total number of stars in the universe. Data from the book: The estimated number of stars in the observable universe is 2×10^23. Calculation: If you count one star every second, the total time in seconds will be equal to the total number of stars. Answer: It would take 𝟐×〖𝟏𝟎〗^𝟐𝟑 seconds to count all the stars in the universe. Question (ii) - Page 42 Calculate and write the answer using scientific notation: (ii) If one could drink a glass of water (200 ml) every 10 seconds, how long would it take to finish the entire volume of water on Earth?This calculation requires a few steps: find the total volume of water, determine how many glasses that is, and then calculate the total time. Data from the book: There are an estimated 2×10^25 drops of water on Earth, assuming 16 drops per milliliter (ml). Calculation: Find the total volume of water in ml : " Total Drops " /(" Drops per " ml)=(2×10^25)/16=0.125×10^25=𝟏.𝟐𝟓×〖𝟏𝟎〗^𝟐𝟒 " " 𝐦𝐥 Find the number of glasses: Divide the total volume by the volume of one glass (200 ml ). " Total Volume " /" Volume per Glass " =(1.25×10^24)/200=(1.25×10^24)/(2×10^2 ) =0.625×10^22=𝟔.𝟐𝟓×〖𝟏𝟎〗^𝟐 Find the total time: Multiply the number of glasses by the time it takes to drink one ( 10 seconds). (" Number of Glasses " )× 10" seconds "=(6.25×10^21 )×10 =𝟔.𝟐𝟓×〖𝟏𝟎〗^𝟐𝟐 " second" Answer: It would take 𝟔.𝟐𝟓 × 〖𝟏𝟎〗^𝟐𝟐 seconds to drink all the water on Earth. For context, that's nearly two quintillion years-far longer than the age of the universe!