# # significant figures in calculations?

I was taught to use the same number of significant figures in my answer as the piece of data with the lowest number of significant figures, so I was a bit confused when the solutions manual for this problem stated the answer as 2.45ms^-2.

Problem: The acceleration due to gravity at the earth's surface is 9.8ms-2. Calculate the acceleration due to gravity on a planet which has the same mass and twice the radius as the earth.

Here the piece of data with the lowest number of significant figures is 9.8ms-2 (2 sig fig), so shouldn't the answer be 2.5ms-2 and not 2.45ms-2 ?

• So what if the person providing that answer simply wasn't following that rule?
– Name
May 6, 2015 at 11:52
• @Name: But they state it at the start of their book! May 6, 2015 at 11:57
• Ohm stated a law of constant electrical resistance, but as a human he did not have a constant resistance himself. People don't always follow their own rules. =)
– Name
May 6, 2015 at 17:59
• @Name Haha good one, but I can't resist (pun intended) pointing out that Ohm's law applies to a very special situation, whereas the rule given in the book is said to apply to "any physics calculation" May 6, 2015 at 18:43
• More on significant figures. Apr 17, 2016 at 14:14

I think the error arises from the fact that it is common to use $$9.80 m/s^2$$ Perhaps this is what was meant.