Triads/Mental Math
20 40 60
40 (MIDDLE) 20 Both ways
0 120 400
(0) Only 120 Other side 200
0 400 600
(600) 200 away
0 300 600
(MIDDLE) 300 each way
30 40 50
(MIDDLE) 10 away both sides
60 80 100
(MIDDLE) 20 both ways
0 200 450
(200) Only 200 away other side 250
0 450 800
(800) 350 away other side is 450
0 350 900
(0) 350 away other side 550
300 400 500
(MIDDLE) 100 both ways
100 400 600
(600) only 200 away
0 920 1000
1000
0 250 600
(0) Only 250 away other side is 350
0 20 50
(0) 20 away
0 700 900
(900) 200 away
80 - 20 =
60
60 - 20 =
40
40 + 20 =
60
50 + 20 =
70
60 + 10 =
70
600 + 200 =
800
100 + 200 =
300
300 + 300 =
600
400 + 600 =
1000
600 + 200 =
800