The formula to find the perimeter of a rectangle is P= 2(l+w). By substituting what we now knowin to the equation:
•42=2(l+(2/5l)). We can have width represented at (2/5l) because it’s now 2/5 of the length. Now add them together to get a single coefficient for l.
•42= 2(7/5l). Multiplying 7/5 by 2.
42= (14/5l). Multiplying both sides by the reciprocal of 14/5, which is 5/14, to get l by itself.
•l= 15.
Now that we now know the value of l, we know that the length is 15m. To find the width of the answer, we then multiply 15 by 2/5, which equals 6. Therefore, the only third option is correct because the length is 15m and the width is 6m.