Tutorial 029 Algebra Practice

This program illustrates how to give youngsters/oldsters some practice manipulating simple equations :

      REM: Algebra Practice
      REM: Richard Weston 31.05.03
      REM: after Alan Thomas
      MODE0
      R$="Right"
      W$="Wrong"
      @%=4
      REPEAT
        x=RND(20)-10
        REPEAT
          m=RND(10)-5
        UNTIL m<>0
        c=RND(10)-5
        y=(m*x)+c
        PRINT'"If ";
        flag=0
        CASE m OF
          WHEN 1: flag=1
          WHEN -1: flag=1
            PRINT"   -";
        ENDCASE
        IF flag=0 THEN PRINT m;
        PRINT "x";
        IF c<>0 THEN
          IF c>0 PRINT "+";ELSE PRINT"-";
          PRINT STR$(ABS(c));
        ENDIF
        PRINT" = ";y
        REPEAT
          INPUT'"what is x",A$
        UNTIL A$<>""
        XA=EVAL(A$)
        IF XA=x PRINT' R$ ELSE PRINT' W$
        PRINT'" x is ";x
        PRINT STRING$(39,"-")
      UNTIL FALSE

Here is an amazingly unlikely series of questions and answers :

If   -4x-4 = -36

what is x? 8

Right

x is 8
---------------------------------------

If   -4x-4 = -32

what is x? 7

Right

x is 7
---------------------------------------

If   -4x-4 = 32

what is x? -7

Wrong

x is -9
---------------------------------------

Note that because EVAL is used in the program answers other than the fully calculated one could be input:

---------------------------------------

If   -2x+2 = 20

what is x? (20-2)/-2

Right

x is -9
---------------------------------------

If    4x+2 = 34

what is x? 32/4

Right

x is 8
---------------------------------------

If    3x-3 = 15

what is x? (15+3)/3

Right

x is 6
---------------------------------------

However, if you can do that you can probably go all the way.

Annotated Listing

      REM: Algebra Practice
      REM: Richard Weston 31.05.03
      REM: after Alan Thomas
      MODE0
      R$="Right"
      W$="Wrong"
      @%=4 Print formatting
      REPEAT
        x=RND(20)-10
        REPEAT
          m=RND(10)-5
        UNTIL m<>0
        c=RND(10)-5
        y=(m*x)+c Equation of a straight line
        PRINT'"If ";
        flag=0
Here we don't want m = 1 or m = -1 values to print the 1 (in conventional algebraic notation)
        CASE m OF
          WHEN 1: flag=1
          WHEN -1: flag=1
            PRINT"   -";
        ENDCASE
..................................................................................................................
        IF flag=0 THEN PRINT m;
        PRINT "x";
Similarly we don't want a c=0 value to be printed
        IF c< >0 THEN
          IF c>0 PRINT "+";ELSE PRINT"-";
          PRINT STR$(ABS(c));
Use ABS so a minus value does not print the minus sign again
Use STR$ to convert the absolute value of the number c to a string
        ENDIF
        PRINT" = ";y

        REPEAT
          INPUT'"what is x",A$
        UNTIL A$< >""
Avoids an error message if you hit the enter key on its own
        XA=EVAL(A$)
Means you can enter an algebraic expression if desired
        IF XA=x PRINT' R$ ELSE PRINT' W$
        PRINT'" x is ";x
        PRINT STRING$(39,"-")
Draws a line across
      UNTIL FALSE
Keeps giving you questions patiently for ever so you can get really good!

Exercise

Modify the program to repeat each question until you get the right answer without telling you the answer until you give up.
Then send in your solution for publication....

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