Estimating and approximating

Estimate these curious quantities sufficiently accurately that you can rank them in order of size

Work out the numerical values for these physical quantities.

In this twist on the well-known Countdown numbers game, use your knowledge of Powers and Roots to make a target.

What do you notice about the date 03.06.09? Or 08.01.09? This challenge invites you to investigate some interesting dates yourself.

Use your skill and knowledge to place various scientific lengths in order of size. Can you judge the length of objects with sizes ranging from 1 Angstrom to 1 million km with no wrong attempts?

How far away was the lightning if the flash and the thunderclap were 6 seconds apart?

Weekly Problem 40 - 2008
A class raises money for charity by placing 10p pieces edge to edge in a 'silver line'. If the line was 25m long, how much money did they make?

From the information you are asked to work out where the picture was taken. Is there too much information? How accurate can your answer be?

See how the motion of the simple pendulum is not-so-simple after all.

How many generations would link an evolutionist to a very distant ancestor?