Posted by vana on .
The shorter side of a rectangle is 20 m. Decreasing the longer side by 30 cm reduces the perimeter by one half. How long are the longer sides of the original rectangle? Explain the reasoning.

grade 6 math 
PsyDAG,
Let S = shorter side, L = longer side and P = perimeter (all in meters).
2S + 2L = P > 40 + 2L = P
2S + 2(L  .3) = P/2 > 40 + 2(L  .3) = P/2
Substitute the value for P from the first equation into the second. Solve for L.
I hope this helps. Thanks for asking.