For this case, we perform the conversions:
First roll:
[tex]1 \ Hectometer --------> 100 \ meters\\3 \ Hectometer --------> x[/tex]
[tex]x = \frac {3 * 100} {1}\\x = 300 \ meters.[/tex]
We make a rule of three to determine the number of "c" boxes that can be packed with 300 meters of adhesive tape.
1 -----------> 4.2
c -----------> 300
[tex]c = \frac {300 * 1} {4.2}\\c = 71.42857143\\c = 71[/tex]
You can pack 71 boxes.
Second roll:
[tex]1 \ Decametro --------> 10 \ meters\\7 \ Decameter --------> x\\x = \frac {7 * 10} {1}\\x = 70 \ meters.[/tex]
We make a rule of three to determine the number of "c" boxes that can be packed with 70 meters of adhesive tape.
1 -----------> 4.2
c -----------> 70
[tex]c = \frac {70 * 1} {4.2}\\c = 16.66666667\\c = 16[/tex]
You can pack 16 boxes.
Third roll:
1 -----------> 4.2
c -----------> 50
[tex]c = \frac {50 * 1} {4.2}\\c = 11.9047619\\c = 11[/tex]
You can pack 11 boxes.
Thus, in total you can pack[tex]11 + 16 + 71 = 98 \ boxes[/tex]
Answer:
98 boxes
