Question

A layer of a sedimentary rock is 2 m thick. How many years did it take for this layer to form if an average of 4 mm of sediment accumulated per year?

Answer 1

`500` years

Explanation:

There are `1000` `mm` in a meter. Now, as layer of sedimentary rock is `2` meters thick, we can say

it is `2xx1000=2000` `mm` tick

Now as `4mm` sediment accumulated every year,

it takes `2000/4=500` years to form this layer.