Today's concept took me a few tries to master, but it was well worth the effort. It has become one of my favorite number sense skills because of the amount of time saved in calculating. This concept has appeared 8 times on middle school tests this year, with a median placement at question # 55.
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Number Dojo Level: 284
The easiest way to recognize this type of problem is that it doesn't fit the other patterns of adding squares we have already discussed (AddSquareTrip and AddSquareDoub). For the skill to work, the problem will be presented as the sum of the squares of two 2-digit numbers:
- The sum of the outer digits (a + d) = 10, and
- The difference of the inner digits (b - c) = 1
How to Solve:
- Verify that the two conditions above are met.
- Square each digit in the first 2-digit number and add the squares together.
- Multiply this result by 101.