How deep?

1½metres

Hi, Kev.

Good try, and not far off. I originally posted this in the Maths forum, as it is difficult. However, they saw fit to move it here. Perhaps it is an indication of where they think/know the brains are.

Try, you need to check your maths mate. Kev's answer is correct.

Adrian, now you have me worried. If I am wrong, apologies all round. My only excuse is I am working off a small portable, without my glasses. This is the result I have.

The worker is 2m tall (200cm). The distance between his head and the ground is equal to 200 - H, where H is the current depth of the hole. The depth of the final hole F is equal to twice the current depth or 2H. When the hole is done, the worker's head will be below ground a distance of F - 200 or 2H - 200.

He says that the distance below ground when the hole is done is twice as much as his head is above ground now. This turns into:
(F - 200) / 2 = 200 - H
F = 2H
(2H - 200) / 2 = 200 - H =
2H - 200 = 400 - 2H
4H = 600
H = 150

This means that the hole is currently 150cm deep. The goal is 300cm. The worker's head is 50cm (200 - 150) above ground now and will be 100cm (300 - 200) below ground when he is done.

Um... 1 and 1/2 metres = 150cm...

All I need is a braille screen and I will be OK!

Tryagain,

Sometimes we all miss the obvious, I'm not all that good at riddles but this one I liked because the answer struck me in 10 seconds flat.

Keep posting em.