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6 ARMY AIR FORCES

 f. In arithmetic, as in other operations, there are many tricks which often simplify the work. One such trick which is useful and easy to remember is the following: To multiply any number by 25, move over the decimal point in the given number two places to the right; then divide by 4.
 Example: Multiply 16.53 by 25
 Solution: Moving the decimal point over two places, 16.53 becomes 1653. Dividing this by 4: 1653/4=413.25. Therefore 16.53x25=413.25  Answer.
 g. Exercises.--To each of the following exercises three answers have been given. Eliminate the answers which are obviously wrong by rounding off the factors and finding the approximately correct answers mentally. 
               {25,632.81
(1) 600.3x42.7={1,200.62
               { 4,273.21
          {30,740
(2)180x76={13,680
          {25,580
              {400.785
(3)12.45x18.3={60.785
              {227.835
          {472.6
(4)88x3.2={281.6
          {31.7
                {63,743.68
(5)1,751.2x36.4={6,374.368
                {12,743.68
             {3,652.925
(6)903x8.475={7,652.925
             {76.52925
 h. Exercises.- perform the indicated multiplications:
(1) .0734 in.x70.34 in.=?
(2) 831.43x71.46=59,413.9878                      Answer.
(3) 1.0073 in.x6.4 ft=?
(4) 8.94x9.37=83.7678                             Answer.
(5) 8,374.5x9,378.46=?
(6)10,742 lbx737.2 ft=7,919,002.4 ft-lb           Answer.
(7) 23.1x847.4=?
(8) 9,034x10.06=90,882.04                         Answer.
(9) 8.037 ftx24.2 lb=?
(10) .0074x371.5=2.7491                            Answer.

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