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A man has a physical balance and a stone of mass 40 kg . He divides the stone into four parts A,B,C,D of mass a kg , b kg , c kg , d kg respectively , such that using A,B,C,D he can measure any specific integral mass from 1 kg to 40 kg . Find the mass of all four parts .i.e., a kg , b kg , c kg , d kg ? {The answer to this question is 1 kg , 3 kg , 9 kg , 27 kg .Explanation: if that man is asked to measure 2kg he will keep 3kg on one of the palm of physical balance and 1 kg on the other . So the net weight being (3-1) kg = 2 kg. For measuring 4 kg he will keep he will use 3kg and 1kg . For measuring 5 kg he will keep 9 kg on one side and 4 kg ( 3kg+1kg ) on the other side . In the same way , he can measure any of the following weights : 1 kg , 2kg , 3kg , ............ 39 kg , 40 kg using those four parts . }. I found this question in a magazine .Though I was able to solve this question using heat and trial method , I did not understand how to solve this question mathematically using algebra or some other convenient mathematical method. Can anyone please solve his question mathematically

A man has a physical balance and a stone of mass 40 kg . He divides the stone into four  parts A,B,C,D of mass a kg , b kg , c kg , d kg respectively , such that using A,B,C,D he can measure any specific integral  mass from 1 kg to 40 kg . Find the mass of all four parts .i.e., a kg , b kg , c kg , d kg ? {The answer to this question is 1 kg , 3 kg , 9 kg , 27 kg .Explanation: if that man is asked to measure 2kg he will keep 3kg on one of the palm of physical balance and 1 kg on the other . So the net weight being (3-1) kg = 2 kg. For measuring 4 kg he will keep he will use 3kg and 1kg . For measuring 5 kg he will keep 9 kg on one side and 4 kg ( 3kg+1kg ) on the other side . In the same way , he can measure any of the following weights : 1 kg , 2kg , 3kg , ............ 39 kg , 40 kg using those four parts .  }.   I found this question in a magazine .Though I was able to solve this question using heat and trial method , I did not understand how to solve this question mathematically using algebra or some other convenient mathematical method. Can anyone please solve his question mathematically

Grade:11

1 Answers

SAGAR SINGH - IIT DELHI
878 Points
13 years ago

Dear student,

I also tried this problem and devoted significant time on this and found out that hit and trial is the best way to solve questions like this..

Please feel free to ask your queries here. We are all IITians and here to help you in your IIT JEE preparation.

All the best.

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Askiitians Expert

Sagar Singh

B.Tech, IIT Delhi

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