Tính bằng cách thuận tiện

Mẫu: 17 + 148 + 32 + 83 = (17 + 83) + (148 + 32)

                                         = 100 + 180

                                         = 280

a) 24 + 17 + 26

b) 80 + 310 + 120

c) 34 + 140 + 60 + 16

Lời giải

a) 24 + 17 + 26 = (24 + 26) + 17

                          = 50 + 17

                          = 67

b) 80 + 310 + 120 = (80 + 120) + 310

                              = 200 + 310

                              = 510

c) 34 + 140 + 60 + 16 = (34 + 16) + (140 + 60)

                                    = 50 + 200

                                    = 250