# 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 + - / * ? Commented Apr 12, 2017 at 16:50
• Anything. It could even be sine or cosine Commented Apr 12, 2017 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. Commented Apr 12, 2017 at 16:55
• Found it. It's the second number in the list. Commented Apr 12, 2017 at 17:04
• To eliminate Ian's solution: does each of the four numbers have to be used exactly once? Commented Apr 12, 2017 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). Commented Apr 12, 2017 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? Commented Apr 12, 2017 at 17:14
• @SamuelMartin: A better question is how can anybody not get the answer.
– Name
Commented Apr 12, 2017 at 17:18
• @Name that's not really an explanation, Samuel is just asking how you thought of this Commented Apr 12, 2017 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. Commented Apr 12, 2017 at 23:05
• @Name can you please explain what's going on in your fourth solution? Commented Apr 12, 2017 at 23:05

My answer is to do this which is shown below

25%(6*8*9)

• How does this work? Commented Apr 12, 2017 at 18:16
• mod means remainder when divided by, the remainder when 25 is divided by 432 is 25 Commented Apr 12, 2017 at 18:21
• I think % is only denoted as mod in computer science? Commented Apr 12, 2017 at 23:06
• Yeah, But I believe its still fine as you still get the ans. Commented Apr 12, 2017 at 23:57