Answer
Answer
The speedometer is likely to show the speed is either 36.0 mph or 44.0 mph.
To prove
Formula
Where error = |Approx value - Exact value |
First case
As given
A speedometer has a percent error of 10%. The actual speed of the car is 40 mph.
Here
Percentage error = 10%
Exact value = 40 mph
error = - (Approx value - Exact value )
= - (Approx value - 40 )
= - Approx value + 40
Put in the formula
Thus
Approx value = 40 - 4
Approx value = 36 mph
Therefore Option (b) is correct .
Second Case
error = (Approx value - Exact value )
= (Approx value - 40 )
= Approx value - 40
Put in the formula
Thus
Approx value = 40 + 4
Approx value = 44 mph
Therefore Option (c) is correct .