4 weights problem Solution

  Problem

Using digits 1, 3, 9, 27  and symbols + or -, we can get 40 in the following way

1 = 1

2= 3-1

3=3

4= 3+1

5= 9- (3+1)

6 = 9 – 3

7 = 9+1-3

8 = 9-1

9=9

10= 9+1

11= 9+3-1

12= 9+3

13= 9+3+1

14= 27 – (9+3+1)

15= 27- (9+3)

16= 27+1-(9+3)

17= 27- (9+1)

18= 27-9

19= 27+1-9

20= 27+3- (9+1)

21= 27+3- 9

22= 27+1+3-9

23= 27- (3+1)

24= 27-3

25= 27+1-3

26= 27-1

27= 27

28=27+1

29= 27+3-1

30= 27+3

31= 27+3+1

32= 27+9- (3+1)

33= 27+9-3

34= 27+9+1- 3

35= 27+9-1

36= 27+9

37= 27+9+1

38= 27+9+3-1

39= 3+9+27

40= 1+3+9+27