Math Word Problems Demystified - A Self Teaching Guide

STRATEGY: Solve the equation:

36 x¼ 64 ð 18 
xÞ

36 x¼ 1152 
 64 x

36 xþ 64 x¼ 1152 
 64 xþ 64 x

100 x¼ 1152

1001 x

1001

¼

1152

100

x¼ 11 : 52

Hence the fulcrum must be placed 11.52 feet from the 36-pound weight.

EVALUATION: Check the equation:

WL¼wl

36 ð 11 : 52 Þ¼ 64 ð 18 
 11 : 52 Þ

414 : 72 ¼ 414 : 72

You can place 3 or more weights on a lever and it still can be balanced. If 4

weights are used, two on each side, the equation is

W 1 L 1 þW 2 L 2 ¼w 1 l 1 þw 2 l 2

EXAMPLE:On a 16-foot seesaw Fred, weighing 80 pounds, sits on one end.

Next to Fred sits Bill, weighing 84 pounds. Bill is 4 feet from the fulcrum. On

the other side at the end sits Pete, weighing 95 pounds. Where should Sam,

weighing 75 pounds, sit in order to balance the seesaw?

SOLUTION:

GOAL: You are being asked to find the distance from the fulcrum where

Sam should sit in order to balance the seesaw.

STRATEGY: Letx¼the distance from the fulcrum where Sam needs to sit.

See Figure 16-5.

176 LESSON 16 Solving Lever Problems