The document NCERT Solutions - Chapter 12: Exponents and Powers, Maths, Class 8 | EduRev Notes is a part of the Class 8 Course Mathematics (Maths) Class 8.

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**Exercise 12.1 **

**Question 1: **

**Evaluate: **

**(i) 3 ^{-2}**

**(ii) (-4) ^{-2}**

**(iii) (1/2) ^{-5}**

**Answer 1:**

**Question 2: **

**Simplify and express the result in power notation with positive exponent: **

**Answer 2: **

**Question 3: **

**Find the value of: **

**Answer 3: **

(i)

(ii)

(iii)

(iv)

(v)

**Question 4: **

**Evaluate: **

**Answer 4: **

**Question 5: **

**Answer 5: **

**Question 6: **

**Evaluate: **

**Answer 6: **

= (3-4) = -1

**Question 7: **

**Simplify: **

**Answer 7: **

(i)

(ii)

**Exercise 12.2 **

**Question 1: **

**Express the following numbers in standard form: **

**(i) 0.0000000000085 **

**(ii) 0.00000000000942 **

**(iii) 6020000000000000 **

**(iv) 0.00000000837 **

**(v) 31860000000 **

**Answer 1: **

**Question 2: **

**Express the following numbers in usual form: **

**[i] 3.02 x 10 ^{-6}**

**(ii) 4.5x 10 ^{4}**

**(in) 3 x 10 ^{-8}**

**[iv] 1.0001 x 10 ^{9}**

**(v) 5.8 x 10 ^{12}**

**(vi) 3.61492 x10 ^{6}**

**Answer 2: **

**Question 3: **

**Express the number appearing in the following statements in standard form: **

**(ii) Charge of an electron is 0.000,000,000,000,000,000,16 coulomb. **

**(iii) Size of a bacteria is 0.0000005 m. **

**(iv) Size of a plant cell is 0.00001275 m. **

**(v) Thickness if a thick paper is 0.07 mm. **

**Answer 3: **

**(i)** 1 micron = 1/1000000 = 1/10^{6} = 1 x 10^{-6} m

[ii] Charge of an electron is 0.00000000000000000016 coulombs.

= 0.00000000000000000016 x 10^{19} / 10^{19} = 1.6x10^{-}^{19} coulomb

[iii] Size of bacteria = 0.0000005 = 5/10000000 = 5x10^{-7} m

(iv) Size of a plant cell is 0.00001275 m = 0.00001275 x 10^{5}/10^{5} = 1.245 x 10^{-}^{5} m

(v) Thickness of a tliick paper = 0.07 mm = 7/100 mm = 7/10^{2} = 7 x 10^{-2} mm

**Question 4:**

**In a stack there are 5 books each of thickness 20 mm and 5 paper sheets each of thickness 0.016 mm. What is the total thickness of the stack? **

**Answer 4: **

Thickness of one book = 20 mm

Thickness of 5 books = 20 x 5 = 100 mm

Thickness of one paper = 0.016 mm

Thickness of 5 papers = 0.016 x 5 = 0.08 mm

Total thickness of a stack = 100 + 0.08 = 100.08 mm

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