20 The rectangle ABCD represents a park.
B
Not to scale
40m
A
D
60m
The lines show all the paths in the park.
The circular path is in the centre of the rectangle and has a diameter of 10m.
Calculate the shortest distance from A to C across the park, using only the paths shown.
Bismuth-210 is an isotope that radioactively decays by about 13% each day, meaning 13% of the remaining bismuth-210 transforms into another atom (polonium-210 in this case) each day. if you begin with 233 mg of bismuth-210, how much remains after 8 days?