Question

Carry out the following additions in the easier way, using the known properties.

(1) 273 + 56 + 44
(2) 178 + 593 + 622
(3) 133 + 17 + 650
(4) 5107 + 2950 + 343

Answer 1

(1) 273 + 56 + 44
Since the sum of 56 and 44 is 100, the second and the third numbers are added first.
= 273 + (56 + 44)
= 273 + 100
= 373

(2) 178 + 593 + 622
Since the sum of 78 and 22 formed by the digits in tens and ones place is 100, the first and the third numbers are added first.
= (178 + 622) + 593
= 800 + 593
= 1393

(3) 133 + 17 + 650
Since the sum of 33 (formed by the digits in tens and ones place of 133) and 17 is 50 and we have another 50 (formed by the digits in ones and tens place of 650), the net sum will be 100.
So, we will add the first and the second numbers first.
= (133 + 17) + 650
= 150 + 650
= 800

(4) 5107 + 2950 + 343
Since the sum of 7 (formed by the digit in ones place of 5107) and 43 (formed by the digits in tens and ones place of 343) is 50 and we have another 50 (formed by the digits in tens and ones place of 2950), the net sum is 100.
Hence, we will add the first and the third numbers first.
= (5107 + 343) + 2950
= 5450 + 2950
= 8400