# How do you make 21 using using 1, 5, 6 and 7?

How do you make the number 21 using 1, 5, 6 and 7 and standard arithmetic operations (addition, subtraction, multiplication and division). You can also use parentheses.

You CANNOT combine two numbers. For example, 15 + 6 = 21...you can't combine 1 and 5 to make 15.

There are no complex solutions to this, but for some reason many people have a lot of trouble with this problem. Don't tell me it's impossible because I have the answer.

Also, if you already know the answer, let other people figure it out on their own.

all of these are wrong so far...and no you cannot use a number

you cant do stupid tricks with numbers like turn them around...this is all simple arithmetic!!!

USE EACH NUMBER ONCE!

I have given you all the information needed...If I tell you the answer, you'll be hitting yourself on the head when you realize that it was not that hard.

AHH! I hate people who think that every problem can be solved by just looking at it...NO, it's not that easy, or else I wouldn't have asked it..Those of you who are saying it's impossible, check back in a couple of days to see the answer

I'm not changing the rules, I just forgot a few the first time I wrote the question...do you think I'm like trying to trick you or somethin??

ADDITION, SUBTRACTION, MULTIPLICATION, DIVISION and PARENTHESES...read the question

no, sqrt usually isn't considered part of addition, subtraction, multiplication, division and parentheses

### 7 Answers

- birdwoman1Lv 41 decade agoBest Answer
But this one is CORRECT:

6/(1-(5/7))

WOO HOO!!!!!

Source(s): 2+ hours and a master's degree in math is paying off! :-) - StratmanLv 41 decade ago
((5-1) x 7) - 6 (this equals 22 . . . close!)

oops . . still working on it . . .

Using base 9: 5+6+7=20 . . .then +1 = 21 !!!!!!

OR . . how about: 5 x 6 x 7 x .1=21 !!!!!!!!!

You can't keep changing the rules after someone answers it !

I now discover this has been presented in this forum before several times . . . and there has been no correct answer provided by the person asking the question . . . I have presented two clear and correct answers . . unless you want to change the rules again this has been solved here.

- 1 decade ago
uhmmm. there is a loop hole in your directions, u didnt tell us how many times we could use each number so we could do:

5+5+5+5+1=21 or

5+5+5+7-1=21 or

7+7+7=21 or

6+6+6+1+1+1=21 or an endless number of combinations

if this is not the solution, then i have no clue....

- How do you think about the answers? You can sign in to vote the answer.
- Anonymous1 decade ago
7+5=12 turn it around=21.

- ( Kelly )Lv 71 decade ago
You're not telling us something..... or else many people would've gotten it already.

So therefore, I will be the first to say IT'S IMPOSSIBLE.