median
don steward
mathematics teaching 10 ~ 16

Tuesday, 26 February 2008

rice grains multiplied

one grain of rice weighs between 25mg and 33mg (0.025g and 0.033g)
½ cup of rice is an average portion
this is approximately 2.8 ounces.
1 oz = 28.35 grms.

how many grains of rice in an average portion?




a courtier, appearing to be modest when asked to state the reward he would like for a good deed, asked a king to have one grain of rice placed on the first square of a chessboard and then two on the next, four on the next and so on, doubling for each next square



a chessboard is 8 by 8 squares

when the entire chessboard is filled, there would be

18, 446, 744, 073, 709, 551, 615 grains of rice (i.e. 2 to the power 64 minus 1).

this is 18, 446, 744, 069, 414, 584, 320 in the second half of the board and a mere 4, 294, 967, 295 grains in the first half of the board

in total, there would be a mass of around 534, 955, 578, 137 tonnes

the mass of the earth is around 5, 973, 600, 000, 000, 000, 000, 000 tonnes
so it would need around 13,000 billion 'chessboard' fulls to make up one 'earth'

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