6.9 SAT Math - Digits

Digit problems look different than regular variable problems because they contain capitalized letters instead of lowercase, like this:

Those capitalized letters represent a digit, regardless of place value.   What's a digit?  A digit is the numbers from 0-9, like a telephone or calculator keypad – hence the phrase, "getting someone's digits."

The trick to digit problems is that sometimes, when you are adding two numbers, you will get an answer in which you need to carry the one over to the next column – that's going to change your answers in the middle column.  Basically, the only way to do digits is to Guess and Check.

-SAT Math Hint: Use the information provided!  In the example above, B and A can technically be any numbers they want, but there are only a few combinations that will add up to 7 in the ones place.  Don't waste time trying 1+2, go straight to the good stuff.

Keep your work on digits problems, like all Guess and Check, neat and systematic.  Start with 1 for B and 6 for A.  Does it work?  No.  Try 2 and 5.  Try 3 and 4.  Next, try 4 and 3.  Why bother?  Because sometimes switching the values among the digits will change the answer.  So then move on to 5 and 2, 6 and 1, 7 and 0, etc.

Did you get an answer?  You should have gotten A=8 and B=9.
-SAT Math Tip: Don't forget that you are taking a timed test, and you are not supposed to be having fun!  If you sense that the digit question is taking too long, skip it!  Don't get stubborn about finding the answer just because the math itself is easy.  You'll fall right into the SAT testmakers' traps.