Exercise 2.2
1. Give the results without actually performing the operations using the given information.
(i) 28 × 19 = 532 then 19 × 28 =
(ii) 1 × 47 = 47 then 47 × 1 =
(iii) a × b = c then b × a =
(iv) 58 + 42 = 100 then 42 + 58 =
(v) 85 + 0 = 85 then 0 + 85 =
(vi) a + b = d then b + a =
2. Find the sum by suitable rearrangement:
(i) 238 + 695 + 162
Rearrange the numbers to group pairs that add up to a multiple of 100: 238 +
(ii) 154 + 197 + 46 + 203
Rearrange the numbers to group pairs that add up to a multiple of 100: 154 +
3. Find the product by suitable rearrangement:
(i) 25 × 1963 × 4
Rearrange to group 25 ×
(ii) 20 × 255 × 50 × 6
Rearrange to group
4. Find the value of the following:
(i) 368 × 12 + 18 × 368
=
(ii) 79 × 4319 + 4319 × 11
=
5. Find the product using suitable properties:
(i) 205 × 1989
We can write: 1989 =
205 × (2000 - 11) = 205 × 2000 - 205 × 11 =
(ii) 1991 × 1005
We can write: 1005 =
1991 × (1000 + 5) = 1991 × 1000 + 1991 × 5 =
6. A milk vendor supplies 56 liters of milk in the morning and 44 liters of milk in the evening to a hostel. If the milk costs Rs. 30 per liter, how much money he gets per day?
Total milk supplied per day =
Total cost = Rs liter
The milk vendor gets Rs. 3000 per day.
7. Chandana and Venu purchased 12 note books and 10 note books respectively. The cost of each note book is Rs. 15,then how much amount should they pay to the shop keeper?
Calculating the cost of Chandana's notebooks: 12 × 15 = Rs.
Calculating the cost of Venu's notebooks: 10 × 15 = Rs.
Total amount to be paid: 180 + 150 = Rs.
Chandana and Venu should pay Rs. 330 to the shopkeeper.
8. Match the following:
1991+7 = 7+1991
68×50 = 50×68
1
0
879×(100+30) = 879×100+879×30
Additive identity
Multiplicative identity
Commutative under addition
Distributive property of multiplication over addition
Commutative under multiplication