A section of a boardwalk is made using 15boards. Each board is 9/1/4 inches wide. The total width of the section is 144 inches. The spacing between each board is equal. What is the width of the spacing between each board.

If there are 15 boards there are 14 gaps in-between.

But first, 15 boards each 9 and 1/4th inches so you get a total of 138 inches and 3/4th

If you subtract that from 144 you get 5 inches and 1/4th. The remaining amount is the total of all of the distance from the spacing.

Then you divide that by 14 (number of gaps/spacing in-between.)

So you get. 375 inches. (3/8)

So width of the spacing between each board is 3/8ths of a inch