4 _ 4 _ 4 _ 4 = 20 How?

👨🏻‍🏫 學術台 數學
2009-07-21 12:00 pm
Use any SIGN among [ + , - , * , / ] in the blanks to make answer 20. NOTE: Brackets not allowed...
更新1:

no, Factorials, Roots are not allowed.. only basic '+', '-', 'x','/' are to be used... 4/4+4x4= 17, not 20 as 4/4 =1 & 4x4 =16, bot division & multiplication are done simultaneously, & addition afterwards....

回答 (8)

2009-07-21 12:32 pm
✔ 最佳答案
There is no solution to the problem as you described it (filling in the blanks with +, -, *, or /, and no insertion of brackets allowed)

The following is a list of numbers that it is possible to make by filling in the blanks in 4 _ 4 _ 4 _ 4 with +, -, *, or /:

-60, -16, -15, -8, -7, -3.75, -1, 0, 0.0625, 1, 2, 3.75, 4.25, 7, 8, 9, 15, 16, 17, 24, 32, 60, 68, 256.

The number 20 is not among the possibilities.
參考: Computer program.
👍 0 👎 0
2009-07-21 12:07 pm
Are we allowed :-

4 ! + 4 - 4 - 4 = 20
OR
4 x 4 + √ 4 + √ 4 = 20

ie FOUR FOURS in each case.
👍 1 👎 1
2009-07-21 12:10 pm
4/4+4*4=20
This is right one.
👍 1 👎 2
2009-07-21 12:04 pm
4/4+4*4=20
👍 1 👎 2
2009-07-21 12:51 pm
(4/4 + 4) x 4 = 20
👍 0 👎 0
2009-07-21 12:19 pm
I don't think it's possible.

Addition and subtraction alone will not go above 12.

multiplication and addition and subtraction gets you

4 * 4 + 4 – 4
4 * 4 + 4 + 4
4 * 4 – 4 – 4

and they don't work

triple multiplication will always get too large a number.

4 * 4 * 4 – 4

division will get you always too small a number

4 / 4 + 4 + 4

division combined with multiplication

4 * 4 / 4 + 4
4 / 4 * 4 + 4

double division, doesn't work either

4 / 4 / 4 + 4 = 4 * 4 / 4 + 4

nothing left that I can see

.
👍 0 👎 0
2009-07-21 12:24 pm
4 / 4 + 4 * 4 = 20
👍 0 👎 1
2009-07-21 12:11 pm
square root of 4 + square root of 4 + 4*4. you did not say square roots are not allowed?
👍 0 👎 1


收錄日期: 2021-05-01 12:37:53
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