Page 34 - Math Genius C5

E:\Working\Orange_Education\Math_Genius_5\Open_Files\CHAP_02
\\October 8, 2025 12:09 PM Bharat Arora P-9 Reader _________________________ Date: ___________________74

5 7 9

1 + 2 + 3 + 4 = 10 2 + 3 + 4 + 5 = 14 3 + 4 + 5 + 6 = 18

5 7 9
 The sum of 4 consecutive numbers is equal to 2 times the sum of the middle two numbers.
6 8 10

1 + 2 + 3 + 4 + 5 = 15 2 + 3 + 4 + 5 + 6 = 20 3 + 4 + 5 + 6 + 7 = 25

6 8 10
 The sum of 5 consecutive numbers is equal to 5 times the middle number.

Fast Check
Find the following sums without adding the numbers directly.

(a) 77 + 78 + 79 (b) 33 + 34 + 35 + 36 (c) 51 + 52 + 53 + 54 + 55

Knowledge Desk

There is a famous story about a young boy named Carl Gauss who was asked
to add all the numbers from 1 to 100. Instead of adding them one by one, he
cleverly paired them up: (1 + 100 = 101), (2 + 99 = 101), (3 + 98 = 101), and so
on. He realized there were 50 such pairs, so he simply calculated 50 × 101 to
get the answer, 5050, in just a few moments.

Practice time 2a

1. Add the following.

(a) TL L tth th H T O (b) TL L tth th H T O (c) TL L tth th H T O

5 8 6 7 8 9 4 6 4 6 7 8 4 9 4 0 6 9 8 9 0
+ 2 9 5 3 5 0 7 + 3 4 5 3 5 7 0 + 5 4 5 9 5 0 9

(d) TL L tth th H T O (e) TL L tth th H T O (f) TL L tth th H T O

7 9 8 0 0 3 7 3 8 6 9 7 3 8 7 5 0 3 4
+ 6 7 8 9 8 7 + 3 7 6 9 5 6 + 3 1 5 6 8 2
8 7 6 5
9
4
6 7 8 9
5
2
2. Arrange in columns and then add.
( a) 37,58,491 and 42,45,781 (b) 2,24,32,646 and 4,42,23,116

( c) 7,54,49,458 and 5,01,67,248 (d) 7,89,45,001 and 3,00,45,010

32 Mathematics-5
32
Mathematics-5