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# Weighty Issue

## Question

Take one ball from machine no1, two from machine no2 and so on. Weigh it once. We know how much the total weight should be, if all the balls were right. Compare this to the actual measured weight. If it is 7mg over weight then machine no7 is producing 1mg overweight balls.

A ball bearing factory has 10 machines (machine no.1 to machine no.10),producing steel balls of exactly the same size. To ensure that the machines are producing the right size, a quality inspector routinely weighs the balls with a sensitive weighing machine. A new opening has arisen in the factory for this job. The production manager explains the weighing procedure to all the applicants and poses this problem:

One of the machines has been producing balls that are 1milligram over or under the specified weight . You get to weigh only once. Use as many balls from any/all machines as you wish. After single weighing you should point out which machine is producing the defective balls and report whether the defective balls are 1mg over or under the specified weight.

Chessmaster2011

## 2 answers to this question

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Sorry, I searched ball bearings and could not find the problem on the site. But a similar problem exists in weighing problems section.

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pick one ball from machine 1 2 balls from machine 2 etc till 10 , then weigh them together,the machine no. producing the defective ball =total weight weighed by the 55 ball bearings-55X(weight of ideal ball bearings)

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