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Task

Get 100 as an answer with only four keystrokes on a regular calculator.

Disallowed keys

  • 0
  • 00

Allowed keys

All other than the aforementioned two keys.

Take the below image as a reference. Regular Calculator

Condition

Atleast two operators must be used.

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  • 2
    $\begingroup$ This question can be found a few different times online: in.answers.yahoo.com/question/index?qid=20111021032155AA4ke5E & quora.com/… you have just added the two operator condition $\endgroup$ – n_plum May 9 '17 at 17:40
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    $\begingroup$ Does pressing = count? $\endgroup$ – theonlygusti May 9 '17 at 19:15
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    $\begingroup$ @theonlygusti Yes $\endgroup$ – Nikhil Bhavar May 9 '17 at 19:17
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    $\begingroup$ Might I suggest "only four keystrokes" instead of "only four buttons" in the wording of this. I could easily complete this task using 1=1+ and simply hammer the "=" sign until 100 is shown on the display. Don't make it easy for the devious :) $\endgroup$ – Wossname May 9 '17 at 19:20
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    $\begingroup$ Scientific calculator allowed or basic calculator only? Also, must every press have a purpose? $\endgroup$ – OldBunny2800 May 9 '17 at 22:20
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On my actual junky little calculator, these four button presses give 100:

$1$
$\div$
$\%$
$=$

In fact, any non-zero digit will work. Calculators will just use the current value in the display as the operand if you didn't type a new one, so what you're doing is saying: Start with $1$. Divide it by ... (the still displayed) $1$ turned into $1\%$, or $0.01$. Then hitting $=$ gives the answer of $100$.

Also, try it here:
https://www.theonlinecalculator.com/
which behaves the same way.

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    $\begingroup$ @CalvT 5% is .05. 5 / .05 is still 100. $\endgroup$ – Rubio May 9 '17 at 17:59
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    $\begingroup$ @Rubio I get 20, as I get 5% of 5, which is 0.25, so 5 / 0.25 $\endgroup$ – CalvT May 9 '17 at 18:00
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    $\begingroup$ @Siguza Looks like you hit "$+$" (PLUS) instead of "$\div$" (DIVIDE)? $\endgroup$ – Rubio May 9 '17 at 18:12
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    $\begingroup$ the percent key means "take x% of the preceding result", so 5 / (5%) is 5 / (5% of 5) = 5 / 0.25 = 20 $\endgroup$ – ffao May 9 '17 at 18:13
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    $\begingroup$ @ffao Actually the $\%$ key on a calculator just means "divide by 100", and it does exactly that. (Following addition/subtraction it gets a little weirder, but following multiplication/division that's all it is.) Try it on the calculator site I posted. $5 \div \% =$ will give $100$. $\endgroup$ – Rubio May 9 '17 at 18:17
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It is

1/1%

because

1/1 = 1 and 1 expressed as a percentage would be 100%. Note that I didn't have to press the = sign in my calculator to get to the 100.

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    $\begingroup$ You need to hit = to make this give the result, which would be a fifth keypress $\endgroup$ – Sconibulus May 9 '17 at 17:30
  • $\begingroup$ Unless they mean 'press 4 buttons' meaning any number of presses but you can only use 4 different keys (1, /, %, =) $\endgroup$ – n_plum May 9 '17 at 17:36
  • $\begingroup$ 1 in percentage is 0.01 $\endgroup$ – Nikhil Bhavar May 9 '17 at 17:48
  • $\begingroup$ @Sconibulus Didn't think about it coz my calc calculated it without pressing the = sign :/ $\endgroup$ – manshu May 9 '17 at 18:53
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    $\begingroup$ = is a fifth button press. Similarly, there's 4x25 (which is the one that I came up with, until I saw the OP's comment that mentioned that = counts as a button press. +1 anyway. $\endgroup$ – Shokhet May 10 '17 at 0:04
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I found another solution.

.1 first and second key, 1/x third key, x2 fourth key. You need a calculator with those buttons though.

The OP says that calculator is just for reference, meaning I can use "a regular calculator" that's slightly different? It's the standard calculator that came with my windows 10.

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On the Windows 7 default calculator the following works

1 % = But then again you have to add the / to make it two operators I guess

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    $\begingroup$ Then this is the same as @Rubio's answer, no? $\endgroup$ – boboquack May 9 '17 at 23:31
  • $\begingroup$ Don't you mean 1/%= and not 1%=? $\endgroup$ – Rand al'Thor May 10 '17 at 0:06
  • $\begingroup$ Interesting, this only works if you had been playing with the other method beforehand. Therefore when you hit 1/%= then proceed to hit 1%= it works but not otherwise, can anyone explain what carries over from the first equation to make the second one work? I always assumed it started with a new calculation after you hit equals unless you continue with a new operator. $\endgroup$ – J. Knight May 10 '17 at 21:18
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You can do it with 3 mouse clicks on a virtual claculator (Windows or Mac):

With the calculator in "programmer" mode, base 16 selected, click 6 4 "base 10"

And for the pedants that require 2 "operators":

With the calculator in "programmer" mode, base 16 selected, click 6 4 "base 10" =

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  • $\begingroup$ This doesn't use the keys shown on the reference calculator. $\endgroup$ – boboquack May 10 '17 at 0:04
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    $\begingroup$ -1. Not a "regular calculator", and you did not use two operators, both of which are indicated in the puzzle. $\endgroup$ – Rubio May 10 '17 at 0:04
  • $\begingroup$ @Rubio I know. But lots of answers on this site "band the rules". I still like my answer. $\endgroup$ – Bohemian May 10 '17 at 0:07
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    $\begingroup$ Then I could "bend the rules" by choosing to ignore the rules I don't like also. My solution is thus: $1 \ \ 0 \ \ 0$, et voila. (Yeah, you can't just toss away the rules, or anarchy wins!) $\endgroup$ – Rubio May 10 '17 at 0:09
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    $\begingroup$ There is no lateral thinking tag which means, don't bend the rules to the question. $\endgroup$ – n_plum May 10 '17 at 0:11
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You can press 25 x 4 to get 100.

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    $\begingroup$ That wouldn't work; you'd need to press the = key as well. (The calculator might think you want to type 25x41=) $\endgroup$ – Glorfindel May 9 '17 at 19:57
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    $\begingroup$ (Also doesn't use two operators, as required.) $\endgroup$ – Rubio May 9 '17 at 20:30
  • $\begingroup$ "That wouldn't work; you'd need to press the = key as well." It will work with an RPN calcluator: 25<enter>4* $\endgroup$ – radarbob May 10 '17 at 2:56
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    $\begingroup$ You used five keystrokes total. $\endgroup$ – oemb1905 May 10 '17 at 3:00
  • $\begingroup$ @radarbob Nope, 2, 5, Enter, 4, * is 5 keystrokes. $\endgroup$ – jamesdlin May 11 '17 at 0:46

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