Question

ALWAYS use significant figure rules. Remember that these rules apply to all numbers that are measurements. You travel 20.0 mph for 0.500 hour, 40.0 mph for 1.00 hour, 30.0 mph for 0.500 hour, and 50.0 mph for 2.00 hours. What is the total distance traveled? 200 miles 170 miles 165 miles 160 miles

Answer 1

The actual answer is 165 miles, but using significant figure rules the answer is 200. This is because the sig fig rules are as follows ...
1. Non-zero digits are always significant.
2. Any zeros between two significant digits are significant.
3. A final zero or trailing zeros in the decimal portion ONLY are significant.

So the zeroes in a number like 20 or 23,000 are NOT significant. When you add numbers you must find the addend with the lowest amount of significant figures and round the answer to that. In this case most of the addends only have one sig fig, so you round 165 to 200 to make it only have one sig fig.

Answer 2

Answer : d = 165 miles

Explanation :

We know that $speed=\dfrac{distance}{time}$

If we travel 20.0 mph for 0.500 hour, then distance covered is 10 miles.

If we travel 40.0 mph for 1.00 hour, then distance covered is 40 miles.

If we travel 30.0 mph for 0.500 hour, distance covered is 15 miles.

If we travel 50.0 mph for 2.00 hours, then distance covered is 100 miles.

So, total distance covered will be 165 miles.