CBSE NCERT Solutions for Class 7 Chapter 13

The NCERT solutions provide students a fine preparation strategy in order to prepare for their exam more methodically. Students get a fair idea on the subject, the sort of questions that are possibly asked and the method to answer them.

CBSE NCERT Solutions for Class 7 Maths Chapter 13:

Question-1:

Simplify:
(i) ((2^5)^2 * 7^3 )/ (8^3 7 )
(ii) (25 * 5^2 * t^8)/ ( 10^3 * t^4 )
(iii) (3^5
10^5 *25) / (5^7 * 6^5 )

Solution:

(i) ((2^5)^2 * 7^3 )/ (8^3 7 )
=(2^(5
2) * 7^3) / ((2^3)^3 * 7 )
=( 2^10 * 7^3 ) / ( (2^(33 ) 7 )
= ( 2^10 * 7^3 )/ ( 2^9 * 7 )
= 2^(10-9) * 7 ^(3-1)
= 2^1 * 7^2
= 2 * 49
=98

(ii) (25 * 5^2 * t^8)/ ( 10^3 * t^4 )
=(5^2 * 5^2 * t^8 ) / ( (25) ^3 * t^4 )
=(5^(2+2) * t^8 ) / (2^3 * 5^3 * t^4 )
=( 5^4 * t^8 ) / ( 8
5^3 * t^4 )
=( 5^(4-3) * t^(8-4) ) /8
= 5 ^1 * t^4 /8
=(5t^4 )/8

(iii) (3^5* 10^5 25) / (5^7 * 6^5 )
=(3^5 * (2
5)^5 * 5^2 ) / (5^7 * (2*3)^5 )
=( 3^5 * 2^5 * 5^5 * 5^2 ) / (5^7 * 2^5 * 3^5 )
=(5^5 *5^2)/ 5^7
= 5^(5+2) / 5^7
=5^7 / 5^7
= 1

Question-2:

Write the following numbers in the expanded form :

279404, 3006194, 2806196, 120719, 20068

Solution:

(i)
2,79,404 = 2,00,000 + 70,000 + 9,000 + 400 + 00 +4
= 2 x 100000 + 7 x 10000 + 9 x 1000 + 4 x 100 + 0 x 10 + 4 x1
= 210^5 + 7 10^4 + 9 10^3 + 410^2 + 0*10^1 +4 * 10^0

(ii)
30,06,194 = 30,00,000 + 0 + 0 + 6,000 + 100 + 90 +4
= 3 x 1000000 + 0 x 100000 + 0 x 10000 + 6 x 1000 + 1 x 100 + 9 x 10+ 41
= 3
10^6 + 0 10^5 + 0 10^4 + 6 * 10^3 + 1* 10^2 + 9* 10^1 +4* 10^0

(iii) 28,06,196 = 20,00,000 + 8,00,000 + 0 + 6,000 + 100 + 90 +6
= 2 x 1000000 + 8 x 100000 + 0 x 10000 + 6 x 1000 + 1 x 100 + 9 x 10+61
= 1
10^6 + 8 10^5 + 010^4 + 610^3 + 110^2 + 910^1 + 610^0

(iv) 1,20,719 = 1,00,000 + 20,000 + 0 + 700 + 10 +9
= 1 x 100000 + 2 x 10000 + 0 x 1000 + 7 x 100 + 1 x 10 + 9 x1
=110^5 + 210^4 + 010^3 + 7 10^2 + 110^1 + 910^0

(v) 20,068 = 20,000 + 00 + 00 + 60 +8
= 2 x 10000 + 0 x 1000 + 0 x 100 + 6 x 10 + 8 x1
= 210^4 + 0 10^3 + 0*10^2 + 6 *10^1 + 8 *10^0

Question-3:

Find the number from each of the following expanded forms:
(a) 8 x 10^4 + 6 x 10^3 + 0 x 10^2 + 4 x 10^1 + 5 x10^0
(b) 4 x 10^5 + 5 x 10^3 + 3 x 10^2 + 2 x10^0
(c) 3 x 10^4 + 7 x 10^2 + 5 x10^0
(d) 9 x 10^5 + 2 x 10^2 + 3 x10^1

Solution:
(a)
8 x 10^4 + 6 x 10^3 + 0 x 10^2 + 4 x 10^1 + 5 x10^0
= 8 x 10000 + 6 x 1000 + 0 x 100 + 4 x 10 + 5 x1
= 80000 + 6000 + 0 + 40 +5
= 86,045
(b)
4 x 10^5 + 5 x 10^3 + 3 x 10^2 + 2 x10^0
= 4 x 100000 + 0 x 10000 + 5 x 1000 + 3 x 100 + 0 x 10 + 2 x1
= 400000 + 0 + 5000 + 3000 + 0 +2
=4,05,302
(c)
3 x 10^4 + 7 x 10^2 + 5 x10^0
= 3 x 10000 + 0 x 1000 + 7 x 100 + 0 x 10 + 5 x1
= 30000 + 0 + 700 + 0 +5
=30,705
(d)
9 x 10^5 + 2 x 10^2 + 3 x10^1
= 9 x 100000 + 0 x 10000 + 0 x 1000 + 2 x 100 + 3 x 10 + 0 x1
= 900000 + 0 + 0 + 200 + 30 +0
=9,00,230