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Example 5 - The record of a weather station shows that - Examples

Example 5 - Chapter 15 Class 9 Probability - Part 2

Example 5 - Chapter 15 Class 9 Probability - Part 3

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Example 5 The record of a weather station shows that out of the past 250 consecutive days, its weather forecasts were correct 175 times. (i) What is the probability that on a given day it was correct? The total number of days for which the record is available = 250 Number of days when forecast was correct = 175 P(the forecast was correct on a given day) = (π‘π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘‘π‘Žπ‘¦π‘  π‘“π‘œπ‘Ÿ π‘€β„Žπ‘’π‘› π‘“π‘œπ‘Ÿπ‘’π‘π‘Žπ‘ π‘‘ π‘€π‘Žπ‘  π‘π‘œπ‘Ÿπ‘Ÿπ‘’π‘π‘‘)/(π‘‡π‘œπ‘‘π‘Žπ‘™ π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘‘π‘Žπ‘¦π‘  π‘“π‘œπ‘Ÿ π‘€β„Žπ‘–π‘β„Ž π‘‘β„Žπ‘’ π‘Ÿπ‘’π‘π‘œπ‘Ÿπ‘‘ 𝑖𝑠 π‘Žπ‘£π‘Žπ‘–π‘™π‘Žπ‘π‘™π‘’) = 175/250 = 0.7 Example 5 (Method 1) The record of a weather station shows that out of the past 250 consecutive days, its weather forecasts were correct 175 times. (ii) What is the probability that it was not correct on a given day? The total number of days for which the record is available = 250 The number of days when the forecast was not correct = 250 – 175 = 75 P(the forecast was not correct on a given day) = (π‘π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘‘π‘Žπ‘¦π‘  π‘“π‘œπ‘Ÿ π‘€β„Žπ‘’π‘› π‘“π‘œπ‘Ÿπ‘’π‘π‘Žπ‘ π‘‘ π‘€π‘Žπ‘  π‘›π‘œπ‘‘ π‘π‘œπ‘Ÿπ‘Ÿπ‘’π‘π‘‘)/(π‘‡π‘œπ‘‘π‘Žπ‘™ π‘›π‘’π‘šπ‘π‘’π‘Ÿ π‘œπ‘“ π‘‘π‘Žπ‘¦π‘  π‘“π‘œπ‘Ÿ π‘€β„Žπ‘–π‘β„Ž π‘‘β„Žπ‘’ π‘Ÿπ‘’π‘π‘œπ‘Ÿπ‘‘ 𝑖𝑠 π‘Žπ‘£π‘Žπ‘–π‘™π‘Žπ‘π‘™π‘’) = 75/250 = 0.3 Example 5 (Method 2) The record of a weather station shows that out of the past 250 consecutive days, its weather forecasts were correct 175 times. (ii) What is the probability that it was not correct on a given day? P(the forecast was not correct on a given day) = 1 – P(forecast was correct on a given day) = 1 – 0.7 = 0.3

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.