A student calculates the mean of three time measurements: 0.0124 s, 13.1 ms and 12700 μs12700\ \mu\mathrm{s}12700 μs. What is the mean time in seconds, to three significant figures?
3.82×10−2 s3.82\times10^{-2}\ \mathrm{s}3.82×10−2 s
1.27×10−2 s1.27\times10^{-2}\ \mathrm{s}1.27×10−2 s
1.27×10−3 s1.27\times10^{-3}\ \mathrm{s}1.27×10−3 s
1.28×10−2 s1.28\times10^{-2}\ \mathrm{s}1.28×10−2 s
39 exam-style questions on Edexcel GCSE Physics 1.1 Units and quantities, covering 1.1.1 SI units for physical quantities and 1.1.2 Unit prefixes, conversions, significant figures and standard form. Each one has a worked solution and a mark scheme showing where the marks go.