Quick questions on Working with scale and data: map scale, rates, graphs and the epicentre calculation - Eduqas GCSE Geology

A map scale tells you how map distance relates to real distance. A scale of $1{:}50\,000$ means $1$ unit on the map equals $50\,000$ units on the ground, so $1$ cm on the map is $50\,000$ cm $= 0.5$ km in reality.

A rate is an amount of change divided by the time it took:

Field and lab data are summarised with simple statistics:

Ages in years come from the half-life idea: a radioactive parent decays to a daughter at a fixed rate, so the parent-to-daughter ratio gives the number of half-lives, and multiplying by the half-life gives the age. (The detail is in the geochronology dot point; here it is one of the standard quantitative tools.)

On a $1{:}25\,000$ map, $1$ cm represents how much real distance? [1 mark]

A cliff retreats $50$ m in $200$ years. Calculate the average rate of erosion in metres per year. [2 marks]

State why the gap between P-wave and S-wave arrivals can be used to find the distance to an earthquake. [1 mark]