Hey guys
Just need to know, on the SAT/PSAT, a phrase called "Units digit" keeps popping up and I have no idea what it means...Here is an example problem
"The unit digit of the sum of three consecutive integers is 8. What is the units digit of the least of these integers?"
A) 4
B) 5
C) 6
D) 7
E) 8
I know this is noobie stuff but just need to know what it means real quick
Thanks alot
Derg
Let the first number be x. Then the three numbers are x, x + 1, and x + 2. The sum of these is 3x + 3. Call the units digit of x n. So the units digit of the sum will be
3n + 3 = 8 (If 3n + 3 is not greater than 9)
or
3n + 3 - 10 = 3n - 7 = 8 (else)
In the first case we have:
3n + 3 = 8
3n = 5 <-- No such n exists.
In the second case we have:
3n - 7 = 8
3n = 15
n = 5.
Thus the units digit of x (the least of the three numbers) is 5.
-Dan