Читать книгу All the Math You'll Ever Need - Steve Slavin - Страница 25

Find the difference between 293 and 581.

Solution:

To begin, you need to “borrow” and regroup, because you can't subtract 3 from 1. Remember that the 8 tens become 7 tens and the ten we borrowed is added to the 1. Subtract 3 from 11 to get 8.

But this requires another regrouping. Borrow 1 from the 5 hundreds, leaving 4 hundreds, and change the borrowed hundred to 10 tens. Add that to the 7 (not 8) tens and subtract 9 from 17.

Finish by subtracting 2 hundred from the remaining 4 hundred.