Question

A music store offers a prize to a customer who can guess the closest, the number of jelly beans that fill a litre jar on the counter. estimate the number of jelly beans in the jar if 1 jelly bean is approximately 2cm (h) by 1.5 cm in diametre (d)

Answer 1

Assuming a jar of (10cm)³.
Then a crude estimate is to line them up in all three directions:
(10/2)*(10/1.5)*(10/1.5)
=5*6.7*6.7
=225
Note that I have used a fractional number of beans because we don't really line them up perfectly. They will be crossed. Also, the space between two layers could be better used by placing a jellybean in the depression between two beans of the lower layer. This can be automatically done by shaking the jar after it's been filled.

See what others give, hopefully a more refined estimate.

Answer 2

222.2222222222222