School-Safe Puzzle Games

Quick arithmetic puzzle

What digit, used 4 times, can be arranged so as to ad up to 100?

17 Comments to “Quick arithmetic puzzle”


  1. Daniel | Guest

    Five. (5 + 5) x (5 + 5) = 10 x 10 = 100


  2. Sal | Guest

    99 + 9/9 =100


  3. Jonathan Pantiesbrough | Guest

    The number 5. 55+55-5-5=100.


  4. John Lewis Highsmith | Guest

    The digit is 9. Do you digit?


  5. Slavco | Guest

    I think it is number 4:


    0 = 4+4-4-4
    1 = (4+4)/(4+4)
    2 = (4*4)/(4+4)
    3 = (4+4+4)/4
    4 = 4+[(4-4)/4]
    5 = [(4*4)+4]/4
    6 = 4+[(4+4)/4]
    7 = (4+4)-(4/4)
    8 = [(4+4)*4]/4
    9 = (4+4)+(4/4)


    ….


  6. Slavco | Guest

    To get other numbers you need to combine 2 number 4, to make a “44″…


    10 = (44 – 4)/4


    Im guessing that you will also use a square root funcion, which to my opnion shouldn’t be right, because if you are using a square root you would need a number 2 indicating that it is square……..


    The really challenging part would be doing it without a square root….(i’m not even sure if it could be done)


  7. Mark W | Guest

    well… it’s not adding, but 99/.99=100


    as does 88/.88=77/.77=…..=22/.22=11/.11=100


  8. James D. Turner | Guest

    Ques. do powers count! If not then:


    5^4/5 -5*5 = 100


  9. Dan Harris | Guest

    [(5x5)-5] x 5


    or


    P + P + P + P in base 25 or higher, if you absolutely need it to be “addition.”


  10. Scott K | Guest

    9: 99 and 9/9ths


  11. J Tanedo | Guest

    do they have to be whole numbers? (55 – 5) / .5 , i know its probably not it, but meh


  12. J Tanedo | Guest

    oh, nvm, [(5 * 5) - 5] * 5


  13. Ian | Guest

    4
    4!x4+square route of 4+ square route of 4
    \
    (4x3x2x1)


  14. deejam | Guest

    answers : 1+2+3+4+(5*5)+(5*5)+6+7+8+9+10


  15. RK | Profile

    several good answers are up


  16. suineg | Guest

    i think 9 is one answer: 99+(9/9)=100, but another a little bit more complicated is this one (7+7)*(7+7^-1), that became (14)*(7+ 1/7)–>98+2—->100, i used 7 because nobody else used that number, but i think there are plenty of possible answers


  17. Sanjay | Guest

    I’m guessing the question has a play on words, so the answer is 5:


    5 is a digit, arranged like this: 5+5+5+5+5 (or 5×5).


    And if used 4 times: (5 x 5) x 4


    adds up to 100 (25 + 25 + 25 + 25)


    Just my thoughts :)


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