NCERT Class 8
139. A half-life is the amount of time that it takes for a radioactive substance to decay to one half of its original quantity. Suppose radioactive decay causes 300 grams of a substance to decrease to 300 × 2^–3 grams after 3 half-lives. Evaluate 300 × 2^–3 to determine how many grams of the substance are left. Explain why the expression 300 × 2^–n can be used to find the amount of the substance that remains after n half-lives.
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Aug
139. A half-life is the amount of time that it takes for a radioactive substance to decay to one half of its original quantity. Suppose radioactive decay causes 300 grams of a substance to decrease to 300 × 2^–3 grams after 3 half-lives. Evaluate 300 × 2^–3 to determine how many grams of the substance [...]
138. About 230 billion litres of water flows through a river each day. How many litres of water flows through that river in a week? How many litres of water flows through the river in an year? Write your answer in standard notation.
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Aug
138. About 230 billion litres of water flows through a river each day. How many litres of water flows through that river in a week? How many litres of water flows through the river in an year? Write your answer in standard notation. 118. 6^n/6^-2 = 6^3 August 1, 2021 Category: Chapter 12 - Exponents [...]
137. While studying her family’s history. Shikha discovers records of ancestors 12 generations back. She wonders how many ancestors she has had in the past 12 generations. She starts to make a diagram to help her figure this out. The diagram soon becomes very complex.
01
Aug
137. While studying her family’s history. Shikha discovers records of ancestors 12 generations back. She wonders how many ancestors she has had in the past 12 generations. She starts to make a diagram to help her figure this out. The diagram soon becomes very complex. 118. 6^n/6^-2 = 6^3 August 1, 2021 Category: Chapter 12 [...]
136. At the end of the 20th century, the world population was approximately 6.1 × 10^9 people. Express this population in usual form. How would you say this number in words?
01
Aug
136. At the end of the 20th century, the world population was approximately 6.1 × 10^9 people. Express this population in usual form. How would you say this number in words? 136. At the end of the 20th century the world population was approximately 6.1 × 10^9 people. Express this population in usual form. How [...]
135. An electron’s mass is approximately 9.1093826 × 10^–31 kilograms. What is this mass in grams?
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Aug
135. An electron’s mass is approximately 9.1093826 × 10^–31 kilograms. What is this mass in grams? 135. An electron’s mass is approximately 9.1093826 × 10^–31 kilograms. What is this mass in grams? August 1, 2021 Category: Chapter 12 - Exponents and Powers , Maths , NCERT Class 8 ,
134. The volume of the Earth is approximately 7.67 × 10^–7 times the volume of the Sun. Express this figure in usual form.
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Aug
134. The volume of the Earth is approximately 7.67 × 10^–7 times the volume of the Sun. Express this figure in usual form. 134. The volume of the Earth is approximately 7.67 × 10^–7 times the volume of the Sun. Express this figure in usual form. August 1, 2021 Category: Chapter 12 - Exponents and [...]
133. An inch is approximately equal to 0.02543 metres. Write this distance in standard form.
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Aug
133. An inch is approximately equal to 0.02543 metres. Write this distance in standard form. 133. An inch is approximately equal to 0.02543 metres. Write this distance in standard form. August 1, 2021 Category: Chapter 12 - Exponents and Powers , Maths , NCERT Class 8 ,
132. The planet Uranus is approximately 2,896,819,200,000 metres away from the Sun. What is this distance in standard form?
01
Aug
132. The planet Uranus is approximately 2,896,819,200,000 metres away from the Sun. What is this distance in standard form? 000 metres away from the Sun. What is this distance in standard form? 132. The planet Uranus is approximately 2 200 819 896 August 1, 2021 Category: Chapter 12 - Exponents and Powers , Maths , [...]
131. This table shows the mass of one atom for five chemical elements. Use it to answer the question given. (a) Which is the heaviest element? (b) Which element is lighter, Silver or Titanium?
01
Aug
131. This table shows the mass of one atom for five chemical elements. Use it to answer the question given. (a) Which is the heaviest element? (b) Which element is lighter, Silver or Titanium? 131. This table shows the mass of one atom for five chemical elements. Use it to answer the question given. (a) [...]
130. Investigating Solar System The table shows the average distance from each planet in our solar system to the sun.
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Aug
130. Investigating Solar System The table shows the average distance from each planet in our solar system to the sun. 130. Investigating Solar System The table shows the average distance from each planet in our solar system to the sun. August 1, 2021 Category: Chapter 12 - Exponents and Powers , Maths , NCERT Class [...]