Breitling NAVITIMER AUTOMATIC GMT 41 Mode D'emploi page 50

SLIDE-RULE
The computer portion of the watch will require a little time and patience to
master, if the pilot is unfamiliar with standard flight computers . It is actually a
circular slide rule and will make accurate computations involving multiplication
and division in terms of time, distance, fuel consumption and other normal flight
and navigation computations dealing with speed, time and distance .
Inspection of the watch will reveal that there is an outer scale on which will be
found numbers running from 10 to 10 (the figure «10» may be 1 .0, 10, 100 . ) . On
the outer perimeter of the dial of the watch is a second similar scale . Note that
the outer scale will always be related to miles, or miles per hour, feet, or feet per
minute, gallons, or gallons per hour, or any quantity which varies with time .
The inner scale deals with minutes or hours in all problems involving time . At
60 minutes on the inner scale there is an arrow which is marked «MPH» . This is
sometimes known as the «ground speed index» or «hour index» . This index is used
in problems involving any quantity per hour .
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MULTIPLICATION
To multiply with the Navitimer use the unit index (number «10» in red on the inner
scale) . Always set the multiplier (the number by which another is multiplied)
opposite the unit index on the inner scale and read the answer on the outer scale
opposite the multiplicand (number to be multiplied by another) appearing on the
inner scale .
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To multiply 7 x 12, set 12 (the multiplier) on outer scale opposite unit index («10»)
on the inner scale . Opposite 7 (the multiplicand) on the inner scale, read the
answer 84 on the mobile dial .
DIVISION
To divide with Navitimer also use the unit index (red 10) . Place the dividend (the
quantity to be divided by another number) on the outer scale opposite the divisor
(quantity by which another is divided) on the inner scale . Opposite the unit index
(numeral «10» on inner scale), read answer on outer scale .
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