Without adding, find the sum.
(i) 1 + 3 + 5 + 7 + 9
(ii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 +19
(iii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23

Solution:

Sum of Consecutive odd numbers is given.

We know that, sum of the first n odd natural numbers is n²

(i) 1 + 3 + 5 + 7 + 9

Here number of term (n) is 5

Sum = (5)² = 25

(ii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

Here number of term (n) is 10

Sum = (10)² = 100

(iii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23

Here number of term (n) is 12

Sum = (12)² = 144

☛ Check: NCERT Solutions for Class 8 Maths Chapter 6

Video Solution:

Without adding, find the sum. (i) 1 + 3 + 5 + 7 + 9 (ii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 +19 (iii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23

NCERT Solutions for Class 8 Maths Chapter 6 Exercise 6.1 Question 7

Summary:

Without adding, the sum of the following (i) 1 + 3 + 5 + 7 + 9 (ii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 +19 (iii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23 are (i) 25, (ii) 100, and (iii) 144

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• Observe the following pattern and find the missing digits. 112 = 121 1012 = 10201 10012 = 1002001 1000012 = 1....2....1 100000012 = ...........
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