Sect. I.

Problem VI.

Three Numbers being given, to find a fourth in a direct Proportion.

This is called the Rule of Three Direct, and by the Instrument is wrought thus;

    Set the first Number given upon B, to the second upon A, and then against the third Number given upon B, is the fourth Number sought.

    Example: If 8 Quarters of Malt will make 20 Barrels of Strong-Beer, how many Barrels of such Beer will 22 Quarters make?

    Set 8 upon B, to 20 upon A, and then against 22 upon B, is 55 upon A; and so many Barrels will 22 Quarters make, and according to this proportion 24 will make 60 barrels, 28 will make 70, 32 Quarters will make 80 Barrels, &c.

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