Question

A-Frame Bookshelf Do-it-yourselfers can build large-capacity, self-supporting bookshelves that are easy to set up and break down. They are called A-frame bookshelves, because the frame and shelves form an A.

The frame uses four 2-by-4’s, each 8 feet long. They are joined in pairs
by a hinge. Holes are drilled through the 2-by-4’s at 1-foot intervals. Round
dowels, 3 of an inch in diameter, connect the two parts of the frame. 4
The shelves are fastened to the dowels. Each shelf is a constant length longer than the shelf above it. In the six-shelf unit shown above, the top shelf is 4 feet long

Answer 1

...and the bottom shelf is 7 feet 4 inches long.

What is the difference in length between each shelf and the one directly below it?

as well for:

A shorter bookshelf uses 2-by-4’s that are 6 ft long, and has five shelves. The top shelf is 3 ft long and the bottom shelf is 6 ft 8 in. long.

and for:

In a four-shelf bookshelf, the bottom shelf is 8 ft long. The top shelf is 5 ft 11 in. long. How long are the other two shelves?

And last but not least… Suppose the 2-by-4’s are 2 in. thick, the shelves are 8 in. deep, and the dowels are cut flush with the front and back faces of the bookshelf. If the dowels are sold in 4-ft lengths, how many lengths would you have to buy for
the bookcase?

Answer 2

Here is the original, can anyone help me? : (