840/12
Cancel down by '2'
420/6
Cancel down by '2' again
210/3
Cancel down by '3'
70/1 = 70 The answer!!!!!
Another way is to think Remember you muktipokication tables, 7 x 12 = 84 . Hence 70 x 12 = 840
or
84/12 = 7 , Then 'stick a '0' on the end because it is '840'. Hence 70 . This is a quick casual method.
0.0107
0.0036
8
120
0.006
14
40
93.3333
24
0.0405
9.0323
210