NCERT Exercise 2.2 Solution class 6 math
Question (1) Find the sum by suitable rearrangement:
(a) 837 + 208 + 363
Solution
Given, 837 + 208 + 363
Since, whole numbers are closed under addition,
Hence, after rearranging the above expression, we get
837 + 363 + 208
= (837 + 363) + 208
= 1200 + 208 = 1408
Thus, Answer = 1408
(b) 1962 + 453 + 1538 + 647
Solution
Given, 1962 + 453 + 1538 + 647
Since, whole numbers are closed under addition,
Hence, after rearranging the above expression, we get
1962 + 1538 + 453 + 647
= (1962 + 1538) + (453 + 647)
= 3500 + 1100 = 4600
Thus, Answer = 4600
Question (2) Find the product by suitable rearrangement:
(a) 2 × 1768 × 50
Solution
Given, 2 × 1768 × 50
Since, whole numbers are closed under multiplication,
Hence, after rearranging the above expression, we get
= 2 × 50 × 1768
= (2 × 50) × 1768
= 100 × 1768
= 176800
Thus, Answer = 176800
(b) 4 × 166 × 125
Solution
Given, 4 × 166 × 125
Since, whole numbers are closed under multiplication,
Hence, after rearranging the above expression, we get
4 × 125 × 166
= (4 × 125) × 166
= 500 × 166
= 83000
Thus, Answer = 83000
(c) 8 × 291 × 125
Given, 8 × 291 × 125
Since, whole numbers are closed under multiplication,
Hence, after rearranging the above expression, we get
8 × 125 × 291
= (8 × 125) × 291
= 1000 × 291
= 291000
Thus, Answer = 291000
(d) 625 × 279 × 16
Answer
Method: 1
Given, 625 × 279 × 16
By rearranging the given expression, we get
625 × 16 × 279
By using distributive and associative property the above expression can be written as
(600 + 20 + 5) × 16 × 279
= [(600 + 20 + 5) × 16] × 279
= [(600 × 16) + (20 × 16) + (5 × 16)] × 279
= [9600 + 320 + 80] × 279
= [9600 + (320 + 80)] × 279
= [9600 + 400] × 279
= 1000 × 279
= 279000
Thus, Answer = 279000
Method: 2
Given, 625 × 279 × 16
By rearranging the given expression, we get
625 × 16 × 279
By using associative property, the above expression can be written as
(625 × 16) × 279
= 1000 × 279
= 279000
Thus, Answer = 279000
(e) 285 × 5 × 60
Solution
Given, 285 × 5 × 60
Since, whole numbers are closed under multiplication, thus by rearranging the given expression, we get
285 × (5 × 60)
= 285 × 300
Again using distributive property to the above expression, we get
285 × (3 × 100)
= (285 × 3) × 100
= 855 × 100
= 85500
Thus, Answer = 85,500
(f) 125 × 40 × 8 × 25
Solution
Given, 125 × 40 × 8 × 25
By using associative property, we get
= (125 × 40) × (8 × 25)
= 500 × 200
= 1,00,000
Thus, Answer = 1,00,000