Enigma 347: Trellis
From New Scientist #1496, 20th February 1986 [link]
I went out on Tuesday to buy a piece of trellis to cover a gap which I measured 30 inches wide × 48 inches high. Allowing half an inch spare on all sides for fixing, I needed at least 31 inches × 49 inches.
I found at the shop that they sold the stuff in various sizes. Size 5, for instance, which is shown in the picture, has five rows of five studs (on which the whole thing swivels); size 6 has six rows of six studs and so on.
In every size the studs were 5 inches apart along the slats, which were 1 inch wide, with each end rounded off in a semicircle of ½-inch radius centred on the last stud.
When I told the manager my measurements, he said,” I’m afraid size 11 will be just too small. If you pull it out to 31 inches wide, the height will be just short of 49 inches. So you’d better take size 12. We charge 5p per stud, so that will be £7.20… Yes, certainly we’ll change it if the size should be wrong.”
When I got home, I was horrified to find that I had mis-measured the height of the gap. It was really 84 inches, not 48 inches. So I needed 31 inches × 85 inches. Back I went to the shop, where, having done my homework meanwhile, I was able this time to ask myself for the size most economical of trellis that would meet my requirements exactly.
What was the price of this trellis?