1. First, put the range in order and then divide the set into quarters. In this case, quartiles are between numbers.83, 85, 89, l 91, 95, 104, l 112, 118, 118, l 125, 134, 138Q₁ = (89 + 91)/2 = 90Q₂ = (104 + 112)/2 =108Q₃ = (118 + 125)/2 = 121.5Interquartile range (IQR) = Q₃ - Q₁ = 121.5 - 90 IQR = 31.52. To find the standard deviation follow the simple steps.Formula in finding the standard deviation: (see attached file) Step 1. Work out the simple average of the numbers (mean) 212 + 249 + 212 + 248 + 239 + 212 + 216 + 234 + 248 9 = 2070 9mean (μ) = 230 Step 2. Subtract the mean on each number and square the result.212 - 230 = (-18)² = 324249 - 230 = ( 19)² = 361212 - 230 = (-18)² = 324248 - 230 = (18)² = 324239 - 230 = (9)² = 81212 - 230 = (-18)² =324216 - 230 = (-14)² =196234 - 230 = (4)² =16248 - 230 = (18)² =324 Step 3. Add all the squared results and get the mean. 2274 9 Variance = 252.6666667 Step 4. Get the square root of the variance. √252.6666667 = 15.89549202
R = speed in still water r + c = speed with current r - c = speed against current
3.5(r + c) = 70 r + c = 20 c = 20 - r
4(r + c) = distance from pier to pier 5(r - c) = distance from pier to pier 4(r + c) = 5(r - c) 4(r + 20 - r) = 5(r - 20 + r) 80 = 10r - 100 180 = 10r 18 = r The speed in still water is 18 km/hour
