# Find 25 using 6, 25, 9, 8 only

You can only use these numbers once, so not square root or cubed root or anything else.

Good Luck!!

• What other rules are there besides no square root, or cubed root? Can we only use basic + - / * ? Apr 12 '17 at 16:50
• Anything. It could even be sine or cosine Apr 12 '17 at 16:51
• You can only use the numbers once, so because there is no 2 or 3 you can't do square or cubes, but you can use any other operation. Apr 12 '17 at 16:55
• Found it. It's the second number in the list. Apr 12 '17 at 17:04
• To eliminate Ian's solution: does each of the four numbers have to be used exactly once? Apr 12 '17 at 17:11

$25 * (9-8)^6$ ...........................

$25\times\lfloor\log(8+6-9)\rfloor$

or

$25+\lfloor\log\log(8+6-9)\rfloor$

• Also 25 | (9 & 8 & 6). Apr 12 '17 at 17:22

$25^{\left \lfloor log_{9}{6*8} \right \rfloor}$

.

$25^{\left \lfloor log_{8}{6*9} \right \rfloor}$

.

$25^{\left \lfloor log_{6}{\binom{9}{8}} \right \rfloor}$

.

## :)

$\left | 25, \Phi, ,\left \{ \Phi \right \}, \left \{ \left \{ \Phi \right \} \right \}, \cdots \right | + \left | 6, \Phi, ,\left \{ \Phi \right \}, \left \{ \left \{ \Phi \right \} \right \}, \cdots \right | + \left | 8, \Phi, ,\left \{ \Phi \right \}, \left \{ \left \{ \Phi \right \} \right \}, \cdots \right | + \left | 9, \Phi, ,\left \{ \Phi \right \}, \left \{ \left \{ \Phi \right \} \right \}, \cdots \right |$

• How did you get that answer? Apr 12 '17 at 17:14
• @SamuelMartin: A better question is how can anybody not get the answer.
– Name
Apr 12 '17 at 17:18
• @Name that's not really an explanation, Samuel is just asking how you thought of this Apr 12 '17 at 17:32
• IMO once you say "Ah, I'll allow sine and cosine", the whole world of mathematical functions can be thrown at the numbers and nothing can stop you anymore. Apr 12 '17 at 23:05
• @Name can you please explain what's going on in your fourth solution? Apr 12 '17 at 23:05

My answer is to do this which is shown below

25%(6*8*9)

• How does this work? Apr 12 '17 at 18:16
• mod means remainder when divided by, the remainder when 25 is divided by 432 is 25 Apr 12 '17 at 18:21
• I think % is only denoted as mod in computer science? Apr 12 '17 at 23:06
• Yeah, But I believe its still fine as you still get the ans. Apr 12 '17 at 23:57