One way is to add on from the smaller number, firstly, the tenths to make the next whole number, and then the units to make 10.
eg 10 – 6.7
Count on from 6.7 to 7 which is 0.3
Then count on from 7 to 10 which is 3
Answer 3 + 0.3 = 3.3
Another way is to count on the units first and then the tenths, but beware the answer which counts on 4 from 6 to make 10 and than counts on 0.3 as this will result in an answer which is one too many: a common slip-up.
Another way of doing this is to ignore the decimal and think of the question as 100 – 67. Work it out mentally (which is 33) and then convert back to 3.3.
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