Final answer:
To find out how many hours earlier Sanya first checked the thermometer, use the expression 1.4 degrees/hour × x hours = 21 degrees, representing the rate of temperature fall. Dividing 21 degrees by 1.4 degrees/hour gives us x = 15 hours, so she first checked it 15 hours before 6 a.m.
Step-by-step explanation:
The question is asking how to find out how many hours earlier Sanya first checked the thermometer if the temperature was falling at a steady rate of 1.4 degrees every hour and has fallen 21 degrees by 6 a.m. To solve this, you can use a simple algebraic expression.
Step-by-Step Explanation:
Let x be the number of hours before 6 a.m. that Sanya first checked the thermometer. Because the temperature is falling at a rate of 1.4 degrees per hour, we can multiply the number of hours, x, by the rate of fall to find the total temperature decrease. Thus, the expression is:
1.4 degrees/hour × x hours = 21 degrees
Finding the Number of Hours:
To find x, you would divide both sides of the equation by 1.4 degrees/hour:
x = 21 degrees ÷ 1.4 degrees/hour
This gives us:
x = 15 hours
Therefore, Sanya first checked the thermometer 15 hours before 6 a.m.