Batman and Robin go out to play Batman who weighs 90 pounds

Batman and Robin go out to play. Batman, who weighs 90 pounds, sits on one end of a 14-foot teeter-totter. Its balance point is at the center of the board. Robin, who weighs 120 pounds, climbs on the other end and slides toward the center until they balance. What is Robin\'s distance from her end of the teeter-totter when they balance?

Solution

the ends are 7 feet from the center

about center it is 90*7 feet pounds .

let Robin distance be x from center of teeter -tooter. Since they balance,
90*7 = 120*x

x = 90*7 / 120= 21/4 feet = 5.25 feet from the center.

If we count from the other end Robin is 7- 5.25 = 1.75 feet from her end.