Solve missing number problems for subtraction using mental methods

So here we have some missing number subtractions. Now, we might already know how to solve these using column subtraction, but let’s see if we can solve these mentally. So for this first question, []the hundred-thousands digit is the same, and the digits in the hundreds, tens and units are also the same. So, if we ignore these digits, how can you get 15 from 22? You subtract 7, []so our answer is 7,000, because the hundreds, tens and units have stayed the same. So why did the first 2, the one here in the ten-thousands, change to a 1, even though we were subtracting thousands, not ten-thousands? Well, that’s because of exchanging or regrouping: if we look at the thousands digit, we can’t do 2 minus 5, so the ten-thousands digit has to change as well. Now, for this next question, []we can highlight the digits that have changed. So how do you get 95 from 103? You subtract 8, []so our answer is 8,000, because the hundreds, tens and units have stayed the same. Now, you might want to pause the video here, and do 4,103,003 minus 8,000 as a column subtraction, because that will help you understand why three digits have changed, and why highlighting the digits that have changed, like we have done here, has helped us to work out the answer mentally. Now for this last question, what has been subtracted here? []Well, the number is the same, but without the millions digit, []so 2 million has been subtracted.