NCERT Solutions Class 8 Mathematics
Chapter – 12 (Exponents and Powers)
The NCERT Solutions in English Language for Class 8 Mathematics Chapter – 12 Exponents and Powers Exercise 12.2 has been provided here to help the students in solving the questions from this exercise.
Chapter 12: Exponents and Powers
Exercise – 12.2
1. Express the following numbers in standard form.
(i) 0.0000000000085
(ii) 0.00000000000942
(iii) 6020000000000000
(iv) 0.00000000837
(v) 31860000000
Solution –
(i) 0.0000000000085
= 0.0000000000085 ×
= 8.5 ×10-12
(ii) 0.00000000000942
= 0.00000000000942 ×
= 9.42×10-12
(iii) 6020000000000000
= 6020000000000000 ×
= 6.02×1015
(iv) 0.00000000837
= 0.00000000837 ×
= 8.37×10-9
(v) 31860000000
= 31860000000 ×
= 3.186×1010
2. Express the following numbers in the usual form.
(i) 3.02×10-6
(ii) 4.5×104
(iii) 3×10-8
(iv) 1.0001×109
(v) 5.8×1012
(vi) 3.61492×106
Solution –
(i) 3.02×10-6
=
= 0 .00000302
(ii) 4.5×104
= 4.5×10000
= 45000
(iii) 3×10-8
=
= 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
(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 mm
Solution –
(i) 1 micron =
=
= 1×10-6
(ii) Charge of an electron is 0.00000000000000000016 coulombs
= 0.00000000000000000016 ×
= 1.6×10-19 coulomb
(iii) Size of bacteria = 0.0000005
=
=
= 5×10-7 m
(iv) Size of a plant cell is 0.00001275 m
= 0.00001275 ×
= 1.275 × 10-5m
(v) Thickness of a thick paper = 0.07 mm
0.07 mm
=
=
= 7×10-2 mm
4. In a stack, there are 5 books, each having a thickness of 20 mm and 5 paper sheets, each having a thickness of 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 ×