# CBSE NCERT Solutions for Class 8 Chapter 12

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CBSE NCERT Solutions for Class 8 Maths Chapter 12:

Question-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 * 10^12 / 10^12 = 8.5 ×10-12
(ii) 0.00000000000942 = 0.00000000000942 * 10^12 / 10^12 =9.42×10-12
(iii) 6020000000000000 = 6020000000000000 * 10^15/ 10^15 = 6.02×1015
(iv) 0.00000000837 = = 0.00000000837 * 10^9 / 10^9 = 8.37 ×10-9
(v) 31860000000 = 31860000000 * 10^10/ 10^10 = 3.186×1010

Question-2:

Express the following numbers in usual form.
(i) 3.02 x 10-6
(ii) 4.5 x 104
(iii) 3 x 10-8
(iv)1.0001 x 109
(v) 5.8 x 1012
(vi)3.61492 x 106

Solution:

(i)3.02 x 10-6 = 3.02/ 10^6 = 0 .00000302
(ii)4.5 x 104 =4.5 * 10000 = 45000
(iii)3 x 10-8 = 3/10^8 = 0.00000003
(iv)1.0001 x 109 =1000100000
(v)5.8 x 1012 = 5.8 * 1000000000000 = 5800000000000
(vi) 6. 3.61492 x 106 = 3.61492 1000000 = 3614920

Question-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 mm

Solution:

(i) 1 micron = 1/1000000
= 1/10^6
=1×10-6
(ii) Charge of an electron is
0.00000000000000000016 coulombs.
= 0.00000000000000000016 * 10^19 / 10^19
= coulomb
(iii) Size of bacteria = 0.0000005
= 5/10000000 = 5/10^7 = 5 * 10^-7 m
(iv) Size of a plant cell is 0.00001275 m
= 0.00001275 * 10^5/ 10^5 = m
(v) Thickness of a thick paper = 0.07 mm
= 7/100 mm = 7/10^2 = 7* 10^-2 mm