NCERT Solution Class 8th Maths Chapter 10 Exponents and Powers Exercise 10.2

NCERT Solution Class 8th Maths Chapter 10 Exponents and Powers

TextbookNCERT
Class 8th
Subject Mathematics
Chapter10th
Chapter NameExponents and Powers
CategoryClass 8th Maths Solutions 
Medium English
SourceLast Doubt

NCERT Solution Class 8th Maths Chapter 10 Exponents and Powers

Chapter – 10

Exponents and Powers

Exercise 10.2

1. Express the following numbers in standard form.
(i) 0.0000000000085
(ii) 0.00000000000942
(iii) 6020000000000000
(iv) 0.00000000837
(v) 31860000000Solution:
(i) 0.0000000000085 = 0.0000000000085×(1012/1012) = 8.5 ×10-12
(ii) 0.00000000000942 = 0.00000000000942×(1012/1012) = 9.42×10-12
(iii) 6020000000000000 = 6020000000000000×(1015/1015) = 6.02×1015
(iv) 0.00000000837 = 0.00000000837×(109/109) = 8.37×10-9
(v) 31860000000 = 31860000000×(1010/1010) = 3.186×1010
2. Express the following numbers in usual form.
(i) 3.02×10-6
(ii) 4.5×104
(iii)3×10-8
(iv)1.0001×109
(v) 5.8×1012
(vi)3.61492×106Solution:
(i) 3.02×10-6 = 3.02/106 = 0 .00000302
(ii) 4.5×104 = 4.5×10000 = 45000
(iii) 3×10-8 = 3/108 = 0.00000003
(iv) 1.0001×109 = 1000100000
(v) 5.8×1012 = 5.8×1000000000000 = 5800000000000
(vi) 3.61492×106 = 3.61492×1000000 = 3614920
3. Express the number appearing in the following statements in standard form.
(i) 1 micron is equal to 1/1000000 m.
(ii) Charge of an electron is 0.000, 000, 000, 000, 000, 000, 16 coulomb.
(iii) Size of bacteria is 0.0000005 m
(iv)  Size of a plant cell is 0.00001275 m
(v) Thickness of a thick paper is 0.07 mmSolution:

(i) 1 micron = 1/1000000
= 1/106
= 1×10-6

(ii) Charge of an electron is 0.00000000000000000016 coulombs.
= 0.00000000000000000016×1019/1019
= 1.6×10-19 coulomb

(iii) Size of bacteria = 0.0000005
=  5/10000000 = 5/107 = 5×10-7 m

(iv) Size of a plant cell is 0.00001275 m
= 0.00001275×105/105
= 1.275×10-5m

(v) Thickness of a thick paper = 0.07 mm
0.07 mm = 7/100 mm = 7/102 = 7×10-2 mm

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?

Solution:
Thickness of one book = 20 mm
Thickness of 5 books = 20×5 = 100 mm
Thickness of one paper = 0.016 mm
Thickness of 5 papers = 0.016×5 = 0.08 mm
Total thickness of a stack = 100+0.08 = 100.08 mm
= 100.08×102/102 mm

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