Converting to Feet per Hour
Understand the relationship between a statute mile and a nautical mile. A statute mile is what is typically used to measure long distances over land. A statute mile is equal to 5,280 feet. A nautical mile is usually used to measure distances that are across open water or space. A nautical mile is equal to 6,076 feet. Knots are determined by how many nautical miles are being travelled per hour. 1 knot = 1 nautical mile per hour.
Multiply the knots by 6,076. This converts the rate in knots to feet per hour, since there are 6,076 feet in a nautical mile. For example, if a boat is travelling at 17 knots, to find how many feet per hour, calculate 17 × 6 , 076 = 103 , 292 {\displaystyle 17\times 6,076=103,292} 17\times 6,076=103,292.
Divide the feet per hour rate by 5,280. Since there are 5,280 feet in a statute mile, to know how many miles per hour something is traveling, divide the number of feet per hour by 5,280. For example, if a boat is travelling 103,292 feet per hour, to find out how many miles per hour it is travelling, you would calculate 103 , 292 5 , 280 = 19.56 {\displaystyle {\frac {103,292}{5,280}}=19.56} {\frac {103,292}{5,280}}=19.56So, a boat travelling at 17 knots is travelling about 19.56 miles per hour.
Multiplying by the Rate Conversion
Understand the relationship between knots and miles per hour. Both are rates of speed. Something travelling at 1 knot is equal to travelling 1.151 miles per hour.
Set up the conversion formula. Since 1 knot = 1.151 miles per hour, the formula is 1.151 x = y {\displaystyle 1.151x=y} 1.151x=y, where x {\displaystyle x} x equals the rate in knots, and y {\displaystyle y} y equals the rate in miles per hour.
Plug the number of knots into the formula. Make sure you are substituting for the x {\displaystyle x} x value. Multiply to find the number of miles per hour. For example, if the wind is blowing at 20 knots, you would calculate as follows: 1.151 ( 20 ) = y {\displaystyle 1.151(20)=y} 1.151(20)=y 23.02 = y {\displaystyle 23.02=y} 23.02=y.So, if the wind blows at 20 knots, it is going about 23 miles per hour.
Converting Miles Per Hour to Knots
Multiply the miles per hour by 5,280, then divide by 6,076. This converts the rate to feet per hour, since there are 5,280 feet in a statute mile. Dividing by 6,076, the number of feet in a nautical mile, tells you how many knots something is travelling. For example, a boat might be travelling 20 mph. Converting to feet per hour: 20 × 5 , 280 = 105 , 600 {\displaystyle 20\times 5,280=105,600} 20\times 5,280=105,600. Converting to knots: 105 , 600 6 , 076 = 17.38 {\displaystyle {\frac {105,600}{6,076}}=17.38} {\frac {105,600}{6,076}}=17.38. So, a boat travelling 20 mph is travelling at about 17 knots.
Multiply the miles per hour by 0.869. This is the conversion rate, since there are about 0.869 knots per mile. The product will tell you the rate in knots. For example, the wind might be blowing at 25 miles per hour. Simply multiply, or use the formula 0.869 x = y {\displaystyle 0.869x=y} 0.869x=y, where x {\displaystyle x} x equals the rate in miles per hour, and y {\displaystyle y} y equals the rate in knots. 25 ( 0.869 ) = 21.725 {\displaystyle 25(0.869)=21.725} 25(0.869)=21.725 So, wind blowing at 25 mph is blowing at about 22 knots.
Try this sample problem. A red boat is travelling at 15 knots. A blue boat is travelling at 17 miles per hour. Which boat is travelling faster? To convert how fast the blue boat is travelling in mph to knots, multiply by the number of miles per hour by 0.869: 0.869 ( 17 ) = 14.77 knots {\displaystyle 0.869(17)=14.77\;{\text{knots}}} 0.869(17)=14.77\;{\text{knots}} The red boat is travelling at 15 knots; the blue boat is travelling a little less than 15 knots. So the red boat is travelling faster.
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