Thread: writing equations

Ralph has just returned from fishing at Big Lake. He was told that the surface of Big Lake is 31 feet above the surface of Long Lake, a neighboring lake. He has also been told that Long Lake is half as deep as Big Lake, and that the bottom of Long Lake is eight feet below the bottom of Big Lake. He is trying to figure out how deep the two lakes are. What are their depths? If B represents the depth of Big Lake, write an equation that represents the above information.

I think I got it after I drew a diagram. Big Lake is 43 ft deep and Long lake is 23 ft deep.

B - 31 + 8 = 1/2B

then solve for B

Originally Posted by ihavvaquestion

Ralph has just returned from fishing at Big Lake. He was told that the surface of Big Lake is 31 feet above the surface of Long Lake, a neighboring lake. He has also been told that Long Lake is half as deep as Big Lake, and that the bottom of Long Lake is eight feet below the bottom of Big Lake. He is trying to figure out how deep the two lakes are. What are their depths? If B represents the depth of Big Lake, write an equation that represents the above information.

just sketch a diagram with the top of Big Lake 31 metres above the top of Long Lake
and the bottom of Long Lake 8 metres below the bottom of Big Lake.


=========BL

31

..............................============LL


========BL
8
.....................................======LL

The depth of LL is x while the depth of BL is 2x

Hence 2x+8=x+31 since these are two identical ways to measure from the top of BL to the bottom of LL.

Just solve that equation.

Oh right, you almost got it... what's twice 23 ?