Question

Exercise 20
Solve by changing one of the numbers to 100 or its multiples.
(a) 195 +25 (b) 498 + 38 (C) 299 +27
(d) 122 + 199 (e) 18 + 299 (f) 25 + 399​

Answer 1

Step-by-step explanation:

(a) 195 + 25

= (200 - 5) + 25

= (200 + 25) - 5

= 25(8 + 1) - 5

= 25(9) - 5

= 225 - 5

= 220

(b) 498 + 38

= 498 + (100 - 62)

= (498 + 100) - 62

= 2(249 + 50) - 62

= 2(299) - 62

= 598 - 62

= 536

(c) 299 + 27

= (200 + 99) + 27

= 200 + (99 + 27)

= 200 + 9(11 + 3)

= 200 + 9(14)

= 200 + 126

= 326

(d) 122 + 199

= 122 + (100 + 99)

= (122 + 100) + 99

= 2(61 + 50) + 99

= 2(111) + 99

= 222 + 99

= 321

(e) 18 + 299

= 18 + (200 + 99)

= (18 + 200) + 99

= 2(9 + 100) + 99

= 2(109) + 99

= 218 + 99

= 317

(f) 25 + 399

= 25 + (200 + 199)

= (25 + 200) + 199

= 25(1 + 8) + 199

= 25(9) + 199

= 225 + 199

= 424