Given,

Inner radius of the well = 4 m

Depth of the well = 14 m

We know that,

Volume of the cylinder = π r2h

= π × 42 × 14 …. (i)

From the question, it’s told that

The earth taken out from the well is evenly spread all around it to form an embankment

And, the width of the embankment = 3 m

So, the outer radius of the well = 3 + 4 m = 7 m

We know that,

Volume of the hollow embankment = π (R2 – r2) × h

= π × (72 – 42) × h …… (ii)

On equating both the equations (i) and (ii), we get

π × 42 × 14 = π × (72 – 42) × h

h = 42 × 14 / (33)

h = 6.78 m

Therefore, the height of the embankment so formed is 6.78 m.