Amount of Board Feet Solution/Explanation

[Guest]

In a table of board measure of various lengths in feet, width in inches, and thickness as 1 inch. Info included says for boards 1 1/4 in. thick, add 1/4 to amt. in table and do same for any other board thickness.

With greater widths, use the sum of quantities in two columns, the sum of the widths that equal desired width.

Example given:

Determine board feet in a plank 24 feet in length, 16 in. wide, and 2.5 in. thick.

Solution provided;

24 ft. * 6 in. = 12 ft. board measure (from table).

24 ft. * 10 in. = 20 ft. b. m. (from table).

24 ft. * 16 in. * 1 in. = 32 ft. b. m. ( I understand this).

24 ft. * 16 * 2.5 = 80 ft. b. m. I don't understand how the 80 was calculated.

[Guest]

Additional follow-up info:

I ran across some extra reference the plank thickness:

The statement included with original problem says thickness as 1 in. Additional indicates if thickness is more than 1, for instance 2.5, the bd. ft. will be 2.5 times.

24 ft. * 16 in. * 1 in. = 32 ft. b. m.

32 * 2.5 = 80.


Also, in ref. to adding the 1/4 to the quantity:

The thickness is 1 in.; add 1/4 to amt. Given problem has 2.5 in. thick plank. Adding 1.5 to quantity;

24 ft. * 6 in. = 12 ft. b. m.; 12 + 12 + 6 = 30

24 ft. * 10 in. = 20 ft. b. m.; 20 + 20 + 10 = 50

30 + 50 = 80.

Am I on the correct path ?