Hi, there--
THE PROBLEM:
You are thinking of a number. You multiplied it by 2 and added 7. The answer is greater than 13 and less than 21. The number is _________.
A SOLUTION:
This is a good problem for working backwards. You say that your answer is greater than 13
and less than 21 right after you added 7.
So right before you added 7, your answer was greater than 6 and less than 14
because 13-7=6 and 21-7=14.
If your number was between 6 and 14 right after you multiplied by 2, then is must have
been greater than 3 and less than 7 right before you multiplied by 2 because
2 time 3 is 6, and 2 time 7 is 14.
The whole numbers greater than 3 and less than 7 are 4, 5, and 6.
You number is 4, 5 or 6. I can't be more specific than that with the rules you gave.
Hope this helps! Feel free to email if you have any questions.
Mrs. Figgy
math.in.the.vortex@gmail.com
