21. The weight of an object equals its density (weight per unit
         volume) times its volume. What is the weight of a block of 
         lead whose dimensions are 1 foot by 0.5 foot by 0.5 foot ? 
        (Lead density is 708 pounds per cubic foot)

  22. The base of a triangle is 8.8 inches and its height is 3.2 inches.
         If a vertical line is drawn from the top to the base, the line 
         intersects the base 3.9 inches from one corner. What is the
        difference in areas of the two new triangles ?

  23. Starting at rest, the distance an object travels equals 
          of its acceleration times the square of the time it travels. 
         How many feet will a train move in 20 seconds if it accelerates
         at a rate of 90 feet per minute per second ?

  24. The earth has a circumference of about 25,000 miles. If it  
         increased by 1 mile, by how many yards would the 
         earth's radius increase ?

  25. A free-falling object accelerates at a rate of about 32 feet 
        per second per second.  An object dropped off a building 
        hits the ground at a velocity of 112 feet per second.
        How long did it take for the object to hit the ground ?