# Ex 12.2, 4 - Chapter 12 Class 8 Exponents and Powers

Last updated at Dec. 19, 2018 by Teachoo

Ex 12.2

Ex 12.2, 1 (i)

Ex 12.2, 1 (ii) Important

Ex 12.2, 1 (iii)

Ex 12.2, 1 (iv)

Ex 12.2, 1 (v) Important

Ex 12.2, 2 (i) Important

Ex 12.2, 2 (ii)

Ex 12.2, 2 (iii) Important

Ex 12.2, 2 (iv)

Ex 12.2, 2 (v) Important

Ex 12.2, 2 (vi)

Ex 12.2, 3 (i)

Ex 12.2, 3 (ii) Important

Ex 12.2, 3 (iii)

Ex 12.2, 3 (iv) Important

Ex 12.2, 3 (v)

Ex 12.2, 4 Important You are here

Ex 12.2, 4 In a stack there are 5 books each of thickness 20mm and 5 paper sheets each of thickness 0.016 mm. What is the total thickness of the stack. Total thickness = Thickness of books + Thickness of paper sheets Thickness of books Number of books = 5 Thickness of 1 book = 20mm Thickness of 5 books = 5 × 20mm = 100 mm Thickness of paper sheets Number of sheets = 5 Thickness of 1 sheet = 0.016 mm = 16/1000 mm Thickness of 5 sheets = 5 × 16/1000 mm = 80/1000 mm Now, Total thickness = Thickness of books + thickness of paper sheets = 100 + 80/1000 = 100 + 8/100 = (100 × 100 + 8)/100 = (10000 + 8)/100 = 10008/100 = 10008/〖10〗^2 = 10008×〖10〗^(−2) = (1.0008×〖10〗^4 )×〖10〗^(−2) = 1.0008×(〖10〗^4×〖10〗^(−2) ) = 1.0008×〖10〗^(4 + (−2)) = 1.0008×〖10〗^(4 − 2) = 𝟏.𝟎𝟎𝟎𝟖×〖𝟏𝟎〗^𝟐 mm (Using 𝑎^𝑚×𝑎^𝑛=𝑎^(𝑚 + 𝑛))